Method and apparatus for indicating sidelink radio link failure in a wireless communication system

ABSTRACT

A method and apparatus for indicating sidelink (SL) radio link failure (RLF) in a wireless communication system is provided. A first wireless device may initialize the counter to zero upon 1) establishing the PC5-RRC connection with the second wireless device, or 2) configuring or reconfiguring the maximum number of the counter. A first wireless device may increase the counter based on no reception of any acknowledgement to the transmission of the MAC PDU. A first wireless device may indicate Sidelink (SL) Radio Link Failure (RLF) for the PC5-RRC connection based on that the counter reaches the maximum number of the counter.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.17/692,429, filed on Mar. 11, 2022, which is a continuation pursuant to35 U.S.C. § 119(e). of International Application PCT/KR2020/015493, withan international filing date of Nov. 6, 2020, which claims the benefitof Korean Patent Application No. 10-2019-0142096, filed on Nov. 7, 2019,the contents of which are hereby incorporated by reference herein intheir entirety.

BACKGROUND Technical Field

The present disclosure relates to a method and apparatus for indicatingsidelink (SL) radio link failure (RLF) in a wireless communicationsystem.

Related Art

rd generation partnership project (3GPP) long-term evolution (LTE) is atechnology for enabling high-speed packet communications. Many schemeshave been proposed for the LTE objective including those that aim toreduce user and provider costs, improve service quality, and expand andimprove coverage and system capacity. The 3GPP LTE requires reduced costper bit, increased service availability, flexible use of a frequencyband, a simple structure, an open interface, and adequate powerconsumption of a terminal as an upper-level requirement.

Work has started in international telecommunication union (ITU) and 3GPPto develop requirements and specifications for new radio (NR) systems3GPP has to identify and develop the technology components needed forsuccessfully standardizing the new RAT timely satisfying both the urgentmarket needs, and the more long-term requirements set forth by the ITUradio communication sector (ITU-R) international mobiletelecommunications (IMT)-2020 process. Further, the NR should be able touse any spectrum band ranging at least up to 100 GHz that may be madeavailable for wireless communications even in a more distant future.

The NR targets a single technical framework addressing all usagescenarios, requirements and deployment scenarios including enhancedmobile broadband (eMBB), massive machine-type-communications (mMTC),ultra-reliable and low latency communications (URLLC), etc. The NR shallbe inherently forward compatible.

Vehicle-to-everything (V2X) communication is the passing of informationfrom a vehicle to any entity that may affect the vehicle, and viceversa. It is a vehicular communication system that incorporates othermore specific types of communication as vehicle-to-infrastructure (V2I),vehicle-to-network (V2N), vehicle-to-vehicle (V2V),vehicle-to-pedestrian (V2P), vehicle-to-device (V2D) and vehicle-to-grid(V2G).

SUMMARY Technical Objects

A wireless device may establish a unicast link and the associatedPC5-RRC connection with another wireless device in sidelink.

In this case, a wireless device may monitor the quality of the PC5-RRCconnection based on hybrid automatic repeat request (HARQ)retransmissions. In this case, it is unclear how the wireless devicedeclares link failure on the PC5-RRC connection.

Therefore, studies for indicating sidelink (SL) radio link failure (RLF)in a wireless communication system are required.

Technical Solutions

In an aspect, a method performed by a first wireless device in awireless communication system is provided. A first wireless device mayinitialize the counter to zero upon 1) establishing the PC5-RRCconnection with the second wireless device, or 2) configuring orreconfiguring the maximum number of the counter. A first wireless devicemay increase the counter based on no reception of any acknowledgement tothe transmission of the MAC PDU. A first wireless device may indicateSidelink (SL) Radio Link Failure (RLF) for the PC5-RRC connection basedon that the counter reaches the maximum number of the counter.

In another aspect, an apparatus for implementing the above method isprovided.

Technical Effects

The present disclosure can have various advantageous effects.

According to some embodiments of the present disclosure, a wirelessdevice could indicate sidelink (SL) radio link failure (RLF) in awireless communication system efficiently.

For example, a wireless device performing radio link management by usingHARQ feedback can properly detect radio link failure by considering HARQfeedback transmissions from another wireless device.

For example, a UE can properly detect radio link failure by consideringHARQ feedback transmissions from another UE when the UE establishes asidelink connection with a peer UE.

For example, a wireless communication system could properly provideradio link management for sidelink connection for a UE performing HARQtransmissions.

Advantageous effects which can be obtained through specific embodimentsof the present disclosure are not limited to the advantageous effectslisted above. For example, there may be a variety of technical effectsthat a person having ordinary skill in the related art can understandand/or derive from the present disclosure. Accordingly, the specificeffects of the present disclosure are not limited to those explicitlydescribed herein, but may include various effects that may be understoodor derived from the technical features of the present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an example of a communication system to whichimplementations of the present disclosure is applied.

FIG. 2 shows an example of wireless devices to which implementations ofthe present disclosure is applied.

FIG. 3 shows an example of a wireless device to which implementations ofthe present disclosure is applied.

FIG. 4 shows another example of wireless devices to whichimplementations of the present disclosure is applied.

FIG. 5 shows an example of UE to which implementations of the presentdisclosure is applied.

FIGS. 6 and 7 show an example of protocol stacks in a 3GPP basedwireless communication system to which implementations of the presentdisclosure is applied.

FIG. 8 shows a frame structure in a 3GPP based wireless communicationsystem to which implementations of the present disclosure is applied.

FIG. 9 shows a data flow example in the 3GPP NR system to whichimplementations of the present disclosure is applied.

FIGS. 10 and 11 show an example of PC5 protocol stacks to whichimplementations of the present disclosure is applied.

FIG. 12 shows an example of a method for indicating sidelink radio linkfailure in a wireless communication system, according to someembodiments of the present disclosure.

FIG. 13 shows an example of a method for performing data transmission bya UE in a wireless communication system, according to some embodimentsof the present disclosure.

FIG. 14 shows an example of method for sidelink HARQ transmissions andfailure detection from a UE in a wireless communication system,according to some embodiments of the present disclosure.

DETAILED DESCRIPTION

The following techniques, apparatuses, and systems may be applied to avariety of wireless multiple access systems. Examples of the multipleaccess systems include a code division multiple access (CDMA) system, afrequency division multiple access (FDMA) system, a time divisionmultiple access (TDMA) system, an orthogonal frequency division multipleaccess (OFDMA) system, a single carrier frequency division multipleaccess (SC-FDMA) system, and a multicarrier frequency division multipleaccess (MC-FDMA) system. CDMA may be embodied through radio technologysuch as universal terrestrial radio access (UTRA) or CDMA2000. TDMA maybe embodied through radio technology such as global system for mobilecommunications (GSM), general packet radio service (GPRS), or enhanceddata rates for GSM evolution (EDGE). OFDMA may be embodied through radiotechnology such as institute of electrical and electronics engineers(IEEE) 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, or evolved UTRA(E-UTRA). UTRA is a part of a universal mobile telecommunications system(UMTS). 3rd generation partnership project (3GPP) long term evolution(LTE) is a part of evolved UMTS (E-UMTS) using E-UTRA. 3GPP LTE employsOFDMA in DL and SC-FDMA in UL. LTE-advanced (LTE-A) is an evolvedversion of 3GPP LTE.

For convenience of description, implementations of the presentdisclosure are mainly described in regards to a 3GPP based wirelesscommunication system. However, the technical features of the presentdisclosure are not limited thereto. For example, although the followingdetailed description is given based on a mobile communication systemcorresponding to a 3GPP based wireless communication system, aspects ofthe present disclosure that are not limited to 3GPP based wirelesscommunication system are applicable to other mobile communicationsystems.

For terms and technologies which are not specifically described amongthe terms of and technologies employed in the present disclosure, thewireless communication standard documents published before the presentdisclosure may be referenced.

In the present disclosure, “A or B” may mean “only A”, “only B”, or“both A and B”. In other words, “A or B” in the present disclosure maybe interpreted as “A and/or B”. For example, “A, B or C” in the presentdisclosure may mean “only A”, “only B”, “only C”, or “any combination ofA, B and C”.

In the present disclosure, slash (/) or comma (,) may mean “and/or”. Forexample. “A/B” may mean “A and/or B”. Accordingly, “A/B” may mean “onlyA”, “only B”, or “both A and B”. For example, “A, B. C” may mean “A, Bor C”.

In the present disclosure, “at least one of A and B” may mean “only A”,“only B” or “both A and B”. In addition, the expression “at least one ofA or B” or “at least one of A and/or B” in the present disclosure may beinterpreted as same as “at least one of A and B”.

In addition, in the present disclosure. “at least one of A. B and C” maymean “only A”. “only B”, “only C”, or “any combination of A, B and C”.In addition. “at least one of A, B or C” or “at least one of A, B and/orC” may mean “at least one of A, B and C”.

Also, parentheses used in the present disclosure may mean “for example”.In detail, when it is shown as “control information (PDCCH)”, “PDCCH”may be proposed as an example of “control information”. In other words,“control information” in the present disclosure is not limited to“PDCCH”, and “PDDCH” may be proposed as an example of “controlinformation”. In addition, even when shown as “control information(i.e., PDCCH)”, “PDCCH” may be proposed as an example of “controlinformation”.

Technical features that are separately described in one drawing in thepresent disclosure may be implemented separately or simultaneously.

Although not limited thereto, various descriptions, functions,procedures, suggestions, methods and/or operational flowcharts of thepresent disclosure disclosed herein can be applied to various fieldsrequiring wireless communication and/or connection (e.g., 5G) betweendevices.

Hereinafter, the present disclosure will be described in more detailwith reference to drawings. The same reference numerals in the followingdrawings and/or descriptions may refer to the same and/or correspondinghardware blocks, software blocks, and/or functional blocks unlessotherwise indicated.

FIG. 1 shows an example of a communication system to whichimplementations of the present disclosure is applied.

The 5G usage scenarios shown in FIG. 1 are only exemplary, and thetechnical features of the present disclosure can be applied to other 5Gusage scenarios which are not shown in FIG. 1 .

Three main requirement categories for 5G include (1) a category ofenhanced mobile broadband (eMBB), (2) a category of massive machine typecommunication (mMTC), and (3) a category of ultra-reliable and lowlatency communications (URLLC).

Partial use cases may require a plurality of categories for optimizationand other use cases may focus only upon one key performance indicator(KPI). 5G supports such various use cases using a flexible and reliablemethod.

eMBB far surpasses basic mobile Internet access and covers abundantbidirectional work and media and entertainment applications in cloud andaugmented reality. Data is one of 5G core motive forces and, in a 5Gera, a dedicated voice service may not be provided for the first time.In 5G, it is expected that voice will be simply processed as anapplication program using data connection provided by a communicationsystem. Main causes for increased traffic volume are due to an increasein the size of content and an increase in the number of applicationsrequiring high data transmission rate. A streaming service (of audio andvideo), conversational video, and mobile Internet access will be morewidely used as more devices are connected to the Internet. These manyapplication programs require connectivity of an always turned-on statein order to push real-time information and alarm for users. Cloudstorage and applications are rapidly increasing in a mobilecommunication platform and may be applied to both work andentertainment. The cloud storage is a special use case which acceleratesgrowth of uplink data transmission rate. 5G is also used for remote workof cloud. When a tactile interface is used, 5G demands much lowerend-to-end latency to maintain user good experience. Entertainment, forexample, cloud gaming and video streaming, is another core element whichincreases demand for mobile broadband capability. Entertainment isessential for a smartphone and a tablet in any place including highmobility environments such as a train, a vehicle, and an airplane. Otheruse cases are augmented reality for entertainment and informationsearch. In this case, the augmented reality requires very low latencyand instantaneous data volume.

In addition, one of the most expected 5G use cases relates a functioncapable of smoothly connecting embedded sensors in all fields, i.e.,mMTC. It is expected that the number of potential Internet-of-things(IoT) devices will reach 204 hundred million up to the year of 2020. Anindustrial IoT is one of categories of performing a main role enabling asmart city, asset tracking, smart utility, agriculture, and securityinfrastructure through 5G.

URLLC includes a new service that will change industry through remotecontrol of main infrastructure and an ultra-reliable/availablelow-latency link such as a self-driving vehicle. A level of reliabilityand latency is essential to control a smart grid, automatize industry,achieve robotics, and control and adjust a drone.

5G is a means of providing streaming evaluated as a few hundred megabitsper second to gigabits per second and may complement fiber-to-the-home(FTTH) and cable-based broadband (or DOCSIS). Such fast speed is neededto deliver TV in resolution of 4K or more (6K, 8K, and more), as well asvirtual reality and augmented reality. Virtual reality (VR) andaugmented reality (AR) applications include almost immersive sportsgames. A specific application program may require a special networkconfiguration. For example, for VR games, gaming companies need toincorporate a core server into an edge network server of a networkoperator in order to minimize latency.

Automotive is expected to be a new important motivated force in 5Gtogether with many use cases for mobile communication for vehicles. Forexample, entertainment for passengers requires high simultaneouscapacity and mobile broadband with high mobility. This is because futureusers continue to expect connection of high quality regardless of theirlocations and speeds. Another use case of an automotive field is an ARdashboard. The AR dashboard causes a driver to identify an object in thedark in addition to an object seen from a front window and displays adistance from the object and a movement of the object by overlappinginformation talking to the driver. In the future, a wireless moduleenables communication between vehicles, information exchange between avehicle and supporting infrastructure, and information exchange betweena vehicle and other connected devices (e.g., devices accompanied by apedestrian). A safety system guides alternative courses of a behavior sothat a driver may drive more safely drive, thereby lowering the dangerof an accident. The next stage will be a remotely controlled orself-driven vehicle. This requires very high reliability and very fastcommunication between different self-driven vehicles and between avehicle and infrastructure. In the future, a self-driven vehicle willperform all driving activities and a driver will focus only uponabnormal traffic that the vehicle cannot identify. Technicalrequirements of a self-driven vehicle demand ultra-low latency andultra-high reliability so that traffic safety is increased to a levelthat cannot be achieved by human being.

A smart city and a smart home/building mentioned as a smart society willbe embedded in a high-density wireless sensor network. A distributednetwork of an intelligent sensor will identify conditions for costs andenergy-efficient maintenance of a city or a home. Similar configurationsmay be performed for respective households. All of temperature sensors,window and heating controllers, burglar alarms, and home appliances arewirelessly connected. Many of these sensors are typically low in datatransmission rate, power, and cost. However, real-time HD video may bedemanded by a specific type of device to perform monitoring.

Consumption and distribution of energy including heat or gas isdistributed at a higher level so that automated control of thedistribution sensor network is demanded. The smart grid collectsinformation and connects the sensors to each other using digitalinformation and communication technology so as to act according to thecollected information. Since this information may include behaviors of asupply company and a consumer, the smart grid may improve distributionof fuels such as electricity by a method having efficiency, reliability,economic feasibility, production sustainability, and automation. Thesmart grid may also be regarded as another sensor network having lowlatency.

Mission critical application (e.g., e-health) is one of 5G usescenarios. A health part contains many application programs capable ofenjoying benefit of mobile communication. A communication system maysupport remote treatment that provides clinical treatment in a farawayplace. Remote treatment may aid in reducing a barrier against distanceand improve access to medical services that cannot be continuouslyavailable in a faraway rural area. Remote treatment is also used toperform important treatment and save lives in an emergency situation.The wireless sensor network based on mobile communication may provideremote monitoring and sensors for parameters such as heart rate andblood pressure.

Wireless and mobile communication gradually becomes important in thefield of an industrial application. Wiring is high in installation andmaintenance cost. Therefore, a possibility of replacing a cable withreconstructible wireless links is an attractive opportunity in manyindustrial fields. However, in order to achieve this replacement, it isnecessary for wireless connection to be established with latency,reliability, and capacity similar to those of the cable and managementof wireless connection needs to be simplified. Low latency and a verylow error probability are new requirements when connection to 5G isneeded.

Logistics and freight tracking are important use cases for mobilecommunication that enables inventory and package tracking anywhere usinga location-based information system. The use cases of logistics andfreight typically demand low data rate but require location informationwith a wide range and reliability.

Referring to FIG. 1 , the communication system 1 includes wirelessdevices 100 a to 100 f, base stations (BSs) 200, and a network 300.Although FIG. 1 illustrates a 5G network as an example of the network ofthe communication system 1, the implementations of the presentdisclosure are not limited to the 5G system, and can be applied to thefuture communication system beyond the 5G system.

The BSs 200 and the network 300 may be implemented as wireless devicesand a specific wireless device may operate as a BS/network node withrespect to other wireless devices.

The wireless devices 100 a to 100 f represent devices performingcommunication using radio access technology (RAT)(e.g., 5G new RAT (NR))or LTE) and may be referred to as communication/radio/5G devices. Thewireless devices 100 a to 100 f may include, without being limited to, arobot 100 a, vehicles 100 b-1 and 100 b-2, an extended reality (XR)device 100 c, a hand-held device 100 d, a home appliance 100 e, an IoTdevice 100 f, and an artificial intelligence (AI) device/server 400. Forexample, the vehicles may include a vehicle having a wirelesscommunication function, an autonomous driving vehicle, and a vehiclecapable of performing communication between vehicles. The vehicles mayinclude an unmanned aerial vehicle (UAV) (e.g., a drone). The XR devicemay include an AR/VR/Mixed Reality (MR) device and may be implemented inthe form of a head-mounted device (HMD), a head-up display (HUD) mountedin a vehicle, a television, a smartphone, a computer, a wearable device,a home appliance device, a digital signage, a vehicle, a robot, etc. Thehand-held device may include a smartphone, a smartpad, a wearable device(e.g., a smartwatch or a smartglasses), and a computer (e.g., anotebook). The home appliance may include a TV, a refrigerator, and awashing machine. The IoT device may include a sensor and a smartmeter.

In the present disclosure, the wireless devices 100 a to 100 f may becalled user equipments (UEs). A UE may include, for example, a cellularphone, a smartphone, a laptop computer, a digital broadcast terminal, apersonal digital assistant (PDA), a portable multimedia player (PMP), anavigation system, a slate personal computer (PC), a tablet PC, anultrabook, a vehicle, a vehicle having an autonomous traveling function,a connected car, an UAV, an AI module, a robot, an AR device, a VRdevice, an MR device, a hologram device, a public safety device, an MTCdevice, an IoT device, a medical device, a FinTech device (or afinancial device), a security device, a weather/environment device, adevice related to a 5G service, or a device related to a fourthindustrial revolution field.

The UAV may be, for example, an aircraft aviated by a wireless controlsignal without a human being onboard.

The VR device may include, for example, a device for implementing anobject or a background of the virtual world. The AR device may include,for example, a device implemented by connecting an object or abackground of the virtual world to an object or a background of the realworld. The MR device may include, for example, a device implemented bymerging an object or a background of the virtual world into an object ora background of the real world. The hologram device may include, forexample, a device for implementing a stereoscopic image of 360 degreesby recording and reproducing stereoscopic information, using aninterference phenomenon of light generated when two laser lights calledholography meet.

The public safety device may include, for example, an image relay deviceor an image device that is wearable on the body of a user.

The MTC device and the IoT device may be, for example, devices that donot require direct human intervention or manipulation. For example, theMTC device and the IoT device may include smartmeters, vending machines,thermometers, smartbulbs, door locks, or various sensors.

The medical device may be, for example, a device used for the purpose ofdiagnosing, treating, relieving, curing, or preventing disease. Forexample, the medical device may be a device used for the purpose ofdiagnosing, treating, relieving, or correcting injury or impairment. Forexample, the medical device may be a device used for the purpose ofinspecting, replacing, or modifying a structure or a function. Forexample, the medical device may be a device used for the purpose ofadjusting pregnancy. For example, the medical device may include adevice for treatment, a device for operation, a device for (in vitro)diagnosis, a hearing aid, or a device for procedure.

The security device may be, for example, a device installed to prevent adanger that may arise and to maintain safety. For example, the securitydevice may be a camera, a closed-circuit TV (CCTV), a recorder, or ablack box.

The FinTech device may be, for example, a device capable of providing afinancial service such as mobile payment. For example, the FinTechdevice may include a payment device or a point of sales (POS) system.

The weather/environment device may include, for example, a device formonitoring or predicting a weather/environment.

The wireless devices 100 a to 100 f may be connected to the network 300via the BSs 200. An AI technology may be applied to the wireless devices100 a to 100 f and the wireless devices 100 a to 10 f may be connectedto the AI server 400 via the network 300. The network 300 may beconfigured using a 3G network, a 4G (e.g., LTE) network, a 5G (e.g., NR)network, and a beyond-5G network. Although the wireless devices 100 a to100 f may communicate with each other through the BSs 200/network 300,the wireless devices 100 a to 100 f may perform direct communication(e.g., sidelink communication) with each other without passing throughthe BSs 200/network 300. For example, the vehicles 100 b-1 and 100 b-2may perform direct communication (e.g., vehicle-to-vehicle(V2V)/vehicle-to-everything (V2X) communication). The IoT device (e.g.,a sensor) may perform direct communication with other IoT devices (e.g.,sensors) or other wireless devices 100 a to 100 f.

Wireless communication/connections 150 a, 150 b and 150 c may beestablished between the wireless devices 100 a to 100 f and/or betweenwireless device 100 a to 100 f and BS 200 and/or between BSs 200.Herein, the wireless communication/connections may be establishedthrough various RATs (e.g., 5G NR) such as uplink/downlink communication150 a, sidelink communication (or device-to-device (D2D) communication)150 b, inter-base station communication 150 c (e.g., relay, integratedaccess and backhaul (IAB)), etc. The wireless devices 100 a to 100 f andthe BSs 200/the wireless devices 100 a to 100 f may transmit/receiveradio signals to/from each other through the wirelesscommunication/connections 150 a, 150 b and 150 c. For example, thewireless communication/connections 150 a, 150 b and 150 c maytransmit/receive signals through various physical channels. To this end,at least a part of various configuration information configuringprocesses, various signal processing processes (e.g., channelencoding/decoding, modulation/demodulation, and resourcemapping/de-mapping), and resource allocating processes, fortransmitting/receiving radio signals, may be performed based on thevarious proposals of the present disclosure.

Here, the radio communication technologies implemented in the wirelessdevices in the present disclosure may include narrowbandinternet-of-things (NB-IoT) technology for low-power communication aswell as LTE, NR and 6G. For example, NB-IoT technology may be an exampleof low power wide area network (LPWAN) technology, may be implemented inspecifications such as LTE Cat NB1 and/or LTE Cat NB2, and may not belimited to the above-mentioned names. Additionally and/or alternatively,the radio communication technologies implemented in the wireless devicesin the present disclosure may communicate based on LTE-M technology. Forexample, LTE-M technology may be an example of LPWAN technology and becalled by various names such as enhanced machine type communication(eMTC). For example, LTE-M technology may be implemented in at least oneof the various specifications, such as 1) LTE Cat 0, 2) LTE Cat M1, 3)LTE Cat M2, 4) LTE non-bandwidth limited (non-BL), 5) LTE-MTC, 6) LTEMachine Type Communication, and/or 7) LTE M, and may not be limited tothe above-mentioned names. Additionally and/or alternatively, the radiocommunication technologies implemented in the wireless devices in thepresent disclosure may include at least one of ZigBee, Bluetooth, and/orLPWAN which take into account low-power communication, and may not belimited to the above-mentioned names. For example, ZigBee technology maygenerate personal area networks (PANs) associated with small/low-powerdigital communication based on various specifications such as IEEE802.15.4 and may be called various names.

FIG. 2 shows an example of wireless devices to which implementations ofthe present disclosure is applied.

Referring to FIG. 2 , a first wireless device 100 and a second wirelessdevice 200 may transmit/receive radio signals to/from an external devicethrough a variety of RATs (e.g., LTE and NR). In FIG. 2 , {the firstwireless device 100 and the second wireless device 200} may correspondto at least one of {the wireless device 100 a to 100 f and the BS 200},{the wireless device 100 a to 100 f and the wireless device 100 a to 100f} and/or {the BS 200 and the BS 200} of FIG. 1 .

The first wireless device 100 may include one or more processors 102 andone or more memories 104 and additionally further include one or moretransceivers 106 and/or one or more antennas 108. The processor(s) 102may control the memory(s) 104 and/or the transceiver(s) 106 and may beconfigured to implement the descriptions, functions, procedures,suggestions, methods and/or operational flowcharts described in thepresent disclosure. For example, the processor(s) 102 may processinformation within the memory(s) 104 to generate firstinformation/signals and then transmit radio signals including the firstinformation/signals through the transceiver(s) 106. The processor(s) 102may receive radio signals including second information/signals throughthe transceiver(s) 106 and then store information obtained by processingthe second information/signals in the memory(s) 104. The memory(s) 104may be connected to the processor(s) 102 and may store a variety ofinformation related to operations of the processor(s) 102. For example,the memory(s) 104 may store software code including commands forperforming a part or the entirety of processes controlled by theprocessor(s) 102 or for performing the descriptions, functions,procedures, suggestions, methods and/or operational flowcharts describedin the present disclosure. Herein, the processor(s) 102 and thememory(s) 104 may be a part of a communication modem/circuit/chipdesigned to implement RAT (e.g., LTE or NR). The transceiver(s) 106 maybe connected to the processor(s) 102 and transmit and/or receive radiosignals through one or more antennas 108. Each of the transceiver(s) 106may include a transmitter and/or a receiver. The transceiver(s) 106 maybe interchangeably used with radio frequency (RF) unit(s). In thepresent disclosure, the first wireless device 100 may represent acommunication modem/circuit/chip.

The second wireless device 200 may include one or more processors 202and one or more memories 204 and additionally further include one ormore transceivers 206 and/or one or more antennas 208. The processor(s)202 may control the memory(s) 204 and/or the transceiver(s) 206 and maybe configured to implement the descriptions, functions, procedures,suggestions, methods and/or operational flowcharts described in thepresent disclosure. For example, the processor(s) 202 may processinformation within the memory(s)204 to generate thirdinformation/signals and then transmit radio signals including the thirdinformation/signals through the transceiver(s) 206. The processor(s) 202may receive radio signals including fourth information/signals throughthe transceiver(s) 106 and then store information obtained by processingthe fourth information/signals in the memory(s) 204. The memory(s) 204may be connected to the processor(s) 202 and may store a variety ofinformation related to operations of the processor(s) 202. For example,the memory(s) 204 may store software code including commands forperforming a part or the entirety of processes controlled by theprocessor(s) 202 or for performing the descriptions, functions,procedures, suggestions, methods and/or operational flowcharts describedin the present disclosure. Herein, the processor(s) 202 and thememory(s) 204 may be a part of a communication modem/circuit/chipdesigned to implement RAT (e.g., LTE or NR). The transceiver(s) 206 maybe connected to the processor(s) 202 and transmit and/or receive radiosignals through one or more antennas 208. Each of the transceiver(s) 206may include a transmitter and/or a receiver. The transceiver(s) 206 maybe interchangeably used with RF unit(s). In the present disclosure, thesecond wireless device 200 may represent a communicationmodem/circuit/chip.

Hereinafter, hardware elements of the wireless devices 100 and 200 willbe described more specifically. One or more protocol layers may beimplemented by, without being limited to, one or more processors 102 and202. For example, the one or more processors 102 and 202 may implementone or more layers (e.g., functional layers such as physical (PHY)layer, media access control (MAC) layer, radio link control (RLC) layer,packet data convergence protocol (PDCP) layer, radio resource control(RRC) layer, and service data adaptation protocol (SDAP) layer). The oneor more processors 102 and 202 may generate one or more protocol dataunits (PDUs) and/or one or more service data unit (SDUs) according tothe descriptions, functions, procedures, suggestions, methods and/oroperational flowcharts disclosed in the present disclosure. The one ormore processors 102 and 202 may generate messages, control information,data, or information according to the descriptions, functions,procedures, suggestions, methods and/or operational flowcharts disclosedin the present disclosure. The one or more processors 102 and 202 maygenerate signals (e.g., baseband signals) including PDUs. SDUs,messages, control information, data, or information according to thedescriptions, functions, procedures, suggestions, methods and/oroperational flowcharts disclosed in the present disclosure and providethe generated signals to the one or more transceivers 106 and 206. Theone or more processors 102 and 202 may receive the signals (e.g.,baseband signals) from the one or more transceivers 106 and 206 andacquire the PDUs, SDUs, messages, control information, data, orinformation according to the descriptions, functions, procedures,suggestions, methods and/or operational flowcharts disclosed in thepresent disclosure.

The one or more processors 102 and 202 may be referred to ascontrollers, microcontrollers, microprocessors, or microcomputers. Theone or more processors 102 and 202 may be implemented by hardware,firmware, software, or a combination thereof. As an example, one or moreapplication specific integrated circuits (ASICs), one or more digitalsignal processors (DSPs), one or more digital signal processing devices(DSPDs), one or more programmable logic devices (PLDs), or one or morefield programmable gate arrays (FPGAs) may be included in the one ormore processors 102 and 202. descriptions, functions, procedures,suggestions, methods and/or operational flowcharts disclosed in thepresent disclosure may be implemented using firmware or software and thefirmware or software may be configured to include the modules,procedures, or functions. Firmware or software configured to perform thedescriptions, functions, procedures, suggestions, methods and/oroperational flowcharts disclosed in the present disclosure may beincluded in the one or more processors 102 and 202 or stored in the oneor more memories 104 and 204 so as to be driven by the one or moreprocessors 102 and 202. The descriptions, functions, procedures,suggestions, methods and/or operational flowcharts disclosed in thepresent disclosure may be implemented using firmware or software in theform of code, commands, and/or a set of commands.

The one or more memories 104 and 204 may be connected to the one or moreprocessors 102 and 202 and store various types of data, signals,messages, information, programs, code, instructions, and/or commands.The one or more memories 104 and 204 may be configured by read-onlymemories (ROMs), random access memories (RAMs), electrically erasableprogrammable read-only memories (EPROMs), flash memories, hard drives,registers, cash memories, computer-readable storage media, and/orcombinations thereof. The one or more memories 104 and 204 may belocated at the interior and/or exterior of the one or more processors102 and 202. The one or more memories 104 and 204 may be connected tothe one or more processors 102 and 202 through various technologies suchas wired or wireless connection.

The one or more transceivers 106 and 206 may transmit user data, controlinformation, and/or radio signals/channels, mentioned in thedescriptions, functions, procedures, suggestions, methods and/oroperational flowcharts disclosed in the present disclosure, to one ormore other devices. The one or more transceivers 106 and 206 may receiveuser data, control information, and/or radio signals/channels, mentionedin the descriptions, functions, procedures, suggestions, methods and/oroperational flowcharts disclosed in the present disclosure, from one ormore other devices. For example, the one or more transceivers 106 and206 may be connected to the one or more processors 102 and 202 andtransmit and receive radio signals. For example, the one or moreprocessors 102 and 202 may perform control so that the one or moretransceivers 106 and 206 may transmit user data, control information, orradio signals to one or more other devices. The one or more processors102 and 202 may perform control so that the one or more transceivers 106and 206 may receive user data, control information, or radio signalsfrom one or more other devices.

The one or more transceivers 106 and 206 may be connected to the one ormore antennas 108 and 208 and the one or more transceivers 106 and 206may be configured to transmit and receive user data, controlinformation, and/or radio signals/channels, mentioned in thedescriptions, functions, procedures, suggestions, methods and/oroperational flowcharts disclosed in the present disclosure, through theone or more antennas 108 and 208. In the present disclosure, the one ormore antennas may be a plurality of physical antennas or a plurality oflogical antennas (e.g., antenna ports).

The one or more transceivers 106 and 206 may convert received radiosignals/channels, etc., from RF band signals into baseband signals inorder to process received user data, control information, radiosignals/channels, etc., using the one or more processors 102 and 202.The one or more transceivers 106 and 206 may convert the user data,control information, radio signals/channels, etc., processed using theone or more processors 102 and 202 from the base band signals into theRF band signals. To this end, the one or more transceivers 106 and 206may include (analog) oscillators and/or filters. For example, thetransceivers 106 and 206 can up-convert OFDM baseband signals to acarrier frequency by their (analog) oscillators and/or filters under thecontrol of the processors 102 and 202 and transmit the up-converted OFDMsignals at the carrier frequency. The transceivers 106 and 206 mayreceive OFDM signals at a carrier frequency and down-convert the OFDMsignals into OFDM baseband signals by their (analog) oscillators and/orfilters under the control of the transceivers 102 and 202.

In the implementations of the present disclosure, a UE may operate as atransmitting device in uplink (UL) and as a receiving device in downlink(DL). In the implementations of the present disclosure, a BS may operateas a receiving device in UL and as a transmitting device in DL.Hereinafter, for convenience of description, it is mainly assumed thatthe first wireless device 100 acts as the UE, and the second wirelessdevice 200 acts as the BS. For example, the processor(s) 102 connectedto, mounted on or launched in the first wireless device 100 may beconfigured to perform the UE behavior according to an implementation ofthe present disclosure or control the transceiver(s) 106 to perform theUE behavior according to an implementation of the present disclosure.The processor(s) 202 connected to, mounted on or launched in the secondwireless device 200 may be configured to perform the BS behavioraccording to an implementation of the present disclosure or control thetransceiver(s) 206 to perform the BS behavior according to animplementation of the present disclosure.

In the present disclosure, a BS is also referred to as a node B (NB), aneNode B (eNB), or a gNB.

FIG. 3 shows an example of a wireless device to which implementations ofthe present disclosure is applied.

The wireless device may be implemented in various forms according to ause-case/service (refer to FIG. 1 ).

Referring to FIG. 3 , wireless devices 100 and 200 may correspond to thewireless devices 100 and 200 of FIG. 2 and may be configured by variouselements, components, units/portions, and/or modules. For example, eachof the wireless devices 100 and 200 may include a communication unit110, a control unit 120, a memory unit 130, and additional components140. The communication unit 110 may include a communication circuit 112and transceiver(s) 114. For example, the communication circuit 112 mayinclude the one or more processors 102 and 202 of FIG. 2 and/or the oneor more memories 104 and 204 of FIG. 2 . For example, the transceiver(s)114 may include the one or more transceivers 106 and 206 of FIG. 2and/or the one or more antennas 108 and 208 of FIG. 2 . The control unit120 is electrically connected to the communication unit 110, the memory130, and the additional components 140 and controls overall operation ofeach of the wireless devices 100 and 200. For example, the control unit120 may control an electric/mechanical operation of each of the wirelessdevices 100 and 200 based on programs/code/commands/information storedin the memory unit 130. The control unit 120 may transmit theinformation stored in the memory unit 130 to the exterior (e.g., othercommunication devices) via the communication unit 110 through awireless/wired interface or store, in the memory unit 130, informationreceived through the wireless/wired interface from the exterior (e.g.,other communication devices) via the communication unit 110.

The additional components 140 may be variously configured according totypes of the wireless devices 100 and 200. For example, the additionalcomponents 140 may include at least one of a power unit/battery,input/output (I/O) unit (e.g., audio I/O port, video I/O port), adriving unit, and a computing unit. The wireless devices 100 and 200 maybe implemented in the form of, without being limited to, the robot (100a of FIG. 1 ), the vehicles (100 b-1 and 100 b-2 of FIG. 1 ), the XRdevice (100 c of FIG. 1 ), the hand-held device (100 d of FIG. 1 ), thehome appliance (100 e of FIG. 1 ), the IoT device (100 f of FIG. 1 ), adigital broadcast terminal, a hologram device, a public safety device,an MTC device, a medicine device, a FinTech device (or a financedevice), a security device, a climate/environment device, the AIserver/device (400 of FIG. 1 ), the BSs (200 of FIG. 1 ), a networknode, etc. The wireless devices 100 and 200 may be used in a mobile orfixed place according to a use-example/service.

In FIG. 3 , the entirety of the various elements, components,units/portions, and/or modules in the wireless devices 100 and 200 maybe connected to each other through a wired interface or at least a partthereof may be wirelessly connected through the communication unit 110.For example, in each of the wireless devices 100 and 200, the controlunit 120 and the communication unit 110 may be connected by wire and thecontrol unit 120 and first units (e.g., 130 and 140) may be wirelesslyconnected through the communication unit 110. Each element, component,unit/portion, and/or module within the wireless devices 100 and 200 mayfurther include one or more elements. For example, the control unit 120may be configured by a set of one or more processors. As an example, thecontrol unit 120 may be configured by a set of a communication controlprocessor, an application processor (AP), an electronic control unit(ECU), a graphical processing unit, and a memory control processor. Asanother example, the memory 130 may be configured by a RAM, a DRAM, aROM, a flash memory, a volatile memory, a non-volatile memory, and/or acombination thereof.

FIG. 4 shows another example of wireless devices to whichimplementations of the present disclosure is applied.

Referring to FIG. 4 , wireless devices 100 and 200 may correspond to thewireless devices 100 and 200 of FIG. 2 and may be configured by variouselements, components, units/portions, and/or modules.

The first wireless device 100 may include at least one transceiver, suchas a transceiver 106, and at least one processing chip, such as aprocessing chip 101. The processing chip 101 may include at least oneprocessor, such a processor 102, and at least one memory, such as amemory 104. The memory 104 may be operably connectable to the processor102. The memory 104 may store various types of information and/orinstructions. The memory 104 may store a software code 105 whichimplements instructions that, when executed by the processor 102,perform the descriptions, functions, procedures, suggestions, methodsand/or operational flowcharts disclosed in the present disclosure. Forexample, the software code 105 may implement instructions that, whenexecuted by the processor 102, perform the descriptions, functions,procedures, suggestions, methods and/or operational flowcharts disclosedin the present disclosure. For example, the software code 105 maycontrol the processor 102 to perform one or more protocols. For example,the software code 105 may control the processor 102 may perform one ormore layers of the radio interface protocol.

The second wireless device 200 may include at least one transceiver,such as a transceiver 206, and at least one processing chip, such as aprocessing chip 201. The processing chip 201 may include at least oneprocessor, such a processor 202, and at least one memory, such as amemory 204. The memory 204 may be operably connectable to the processor202. The memory 204 may store various types of information and/orinstructions. The memory 204 may store a software code 205 whichimplements instructions that, when executed by the processor 202,perform the descriptions, functions, procedures, suggestions, methodsand/or operational flowcharts disclosed in the present disclosure. Forexample, the software code 205 may implement instructions that, whenexecuted by the processor 202, perform the descriptions, functions,procedures, suggestions, methods and/or operational flowcharts disclosedin the present disclosure. For example, the software code 205 maycontrol the processor 202 to perform one or more protocols. For example,the software code 205 may control the processor 202 may perform one ormore layers of the radio interface protocol.

FIG. 5 shows an example of UE to which implementations of the presentdisclosure is applied.

Referring to FIG. 5 , a UE 100 may correspond to the first wirelessdevice 100 of FIG. 2 and/or the first wireless device 100 of FIG. 4 .

A UE 100 includes a processor 102, a memory 104, a transceiver 106, oneor more antennas 108, a power management module 110, a battery 1112, adisplay 114, a keypad 116, a subscriber identification module (SIM) card118, a speaker 120, and a microphone 122.

The processor 102 may be configured to implement the descriptions,functions, procedures, suggestions, methods and/or operationalflowcharts disclosed in the present disclosure. The processor 102 may beconfigured to control one or more other components of the UE 100 toimplement the descriptions, functions, procedures, suggestions, methodsand/or operational flowcharts disclosed in the present disclosure.Layers of the radio interface protocol may be implemented in theprocessor 102. The processor 102 may include ASIC, other chipset, logiccircuit and/or data processing device. The processor 102 may be anapplication processor. The processor 102 may include at least one of adigital signal processor (DSP), a central processing unit (CPU), agraphics processing unit (GPU), a modem (modulator and demodulator). Anexample of the processor 102 may be found in SNAPDRAGON™ series ofprocessors made by Qualcomm®, EXYNOS™ series of processors made bySamsung*, A series of processors made by Apple®, HELIO™ series ofprocessors made by MediaTek®, ATOM™ series of processors made by Intel®or a corresponding next generation processor.

The memory 104 is operatively coupled with the processor 102 and storesa variety of information to operate the processor 102. The memory 104may include ROM, RAM, flash memory, memory card, storage medium and/orother storage device. When the embodiments are implemented in software,the techniques described herein can be implemented with modules (e.g.,procedures, functions, etc.) that perform the descriptions, functions,procedures, suggestions, methods and/or operational flowcharts disclosedin the present disclosure. The modules can be stored in the memory 104and executed by the processor 102. The memory 104 can be implementedwithin the processor 102 or external to the processor 102 in which casethose can be communicatively coupled to the processor 102 via variousmeans as is known in the art.

The transceiver 106 is operatively coupled with the processor 102, andtransmits and/or receives a radio signal. The transceiver 106 includes atransmitter and a receiver. The transceiver 106 may include basebandcircuitry to process radio frequency signals. The transceiver 106controls the one or more antennas 108 to transmit and/or receive a radiosignal.

The power management module 110 manages power for the processor 102and/or the transceiver 106. The battery 112 supplies power to the powermanagement module 110.

The display 114 outputs results processed by the processor 102. Thekeypad 116 receives inputs to be used by the processor 102. The keypad16 may be shown on the display 114.

The SIM card 118 is an integrated circuit that is intended to securelystore the international mobile subscriber identity (IMSI) number and itsrelated key, which are used to identify and authenticate subscribers onmobile telephony devices (such as mobile phones and computers). It isalso possible to store contact information on many SIM cards.

The speaker 120 outputs sound-related results processed by the processor102. The microphone 122 receives sound-related inputs to be used by theprocessor 102.

FIGS. 6 and 7 show an example of protocol stacks in a 3GPP basedwireless communication system to which implementations of the presentdisclosure is applied.

In particular, FIG. 6 illustrates an example of a radio interface userplane protocol stack between a UE and a BS and FIG. 7 illustrates anexample of a radio interface control plane protocol stack between a UEand a BS. The control plane refers to a path through which controlmessages used to manage call by a UE and a network are transported. Theuser plane refers to a path through which data generated in anapplication layer, for example, voice data or Internet packet data aretransported. Referring to FIG. 6 , the user plane protocol stack may bedivided into Layer 1 (i.e., a PHY layer) and Layer 2. Referring to FIG.7 , the control plane protocol stack may be divided into Layer 1 (i.e.,a PHY layer), Layer 2, Layer 3 (e.g., an RRC layer), and a non-accessstratum (NAS) layer. Layer 1, Layer 2 and Layer 3 are referred to as anaccess stratum (AS).

In the 3GPP LTE system, the Layer 2 is split into the followingsublayers: MAC, RLC, and PDCP. In the 3GPP NR system, the Layer 2 issplit into the following sublayers: MAC, RLC, PDCP and SDAP. The PHYlayer offers to the MAC sublayer transport channels, the MAC sublayeroffers to the RLC sublayer logical channels, the RLC sublayer offers tothe PDCP sublayer RLC channels, the PDCP sublayer offers to the SDAPsublayer radio bearers. The SDAP sublayer offers to 5G core networkquality of service (QoS) flows.

In the 3GPP NR system, the main services and functions of the MACsublayer include: mapping between logical channels and transportchannels; multiplexing/de-multiplexing of MAC SDUs belonging to one ordifferent logical channels into/from transport blocks (TB) deliveredto/from the physical layer on transport channels; scheduling informationreporting; error correction through hybrid automatic repeat request(HARQ) (one HARQ entity per cell in case of carrier aggregation (CA));priority handling between UEs by means of dynamic scheduling; priorityhandling between logical channels of one UE by means of logical channelprioritization; padding. A single MAC entity may support multiplenumerologies, transmission timings and cells. Mapping restrictions inlogical channel prioritization control which numerology(ies), cell(s),and transmission timing(s) a logical channel can use.

Different kinds of data transfer services are offered by MAC. Toaccommodate different kinds of data transfer services, multiple types oflogical channels are defined, i.e., each supporting transfer of aparticular type of information. Each logical channel type is defined bywhat type of information is transferred. Logical channels are classifiedinto two groups: control channels and traffic channels. Control channelsare used for the transfer of control plane information only, and trafficchannels are used for the transfer of user plane information only.Broadcast control channel (BCCH) is a downlink logical channel forbroadcasting system control information, paging control channel (PCCH)is a downlink logical channel that transfers paging information, systeminformation change notifications and indications of ongoing publicwarning service (PWS) broadcasts, common control channel (CCCH) is alogical channel for transmitting control information between UEs andnetwork and used for UEs having no RRC connection with the network, anddedicated control channel (DCCH) is a point-to-point bi-directionallogical channel that transmits dedicated control information between aUE and the network and used by UEs having an RRC connection. Dedicatedtraffic channel (DTCH) is a point-to-point logical channel, dedicated toone UE, for the transfer of user information. A DTCH can exist in bothuplink and downlink. In downlink, the following connections betweenlogical channels and transport channels exist: BCCH can be mapped tobroadcast channel (BCH); BCCH can be mapped to downlink shared channel(DL-SCH); PCCH can be mapped to paging channel (PCH); CCCH can be mappedto DL-SCH; DCCH can be mapped to DL-SCH; and DTCH can be mapped toDL-SCH. In uplink, the following connections between logical channelsand transport channels exist: CCCH can be mapped to uplink sharedchannel (UL-SCH); DCCH can be mapped to UL-SCH; and DTCH can be mappedto UL-SCH.

The RLC sublayer supports three transmission modes: transparent mode(TM), unacknowledged mode (UM), and acknowledged node (AM). The RLCconfiguration is per logical channel with no dependency on numerologiesand/or transmission durations. In the 3GPP NR system, the main servicesand functions of the RLC sublayer depend on the transmission mode andinclude: transfer of upper layer PDUs; sequence numbering independent ofthe one in PDCP (UM and AM); error correction through ARQ (AM only);segmentation (AM and UM) and re-segmentation (AM only) of RLC SDUs;reassembly of SDU (AM and UM); duplicate detection (AM only); RLC SDUdiscard (AM and UM); RLC re-establishment; protocol error detection (AMonly).

In the 3GPP NR system, the main services and functions of the PDCPsublayer for the user plane include: sequence numbering; headercompression and decompression using robust header compression (ROHC);transfer of user data; reordering and duplicate detection; in-orderdelivery; PDCP PDU routing (in case of split bearers); retransmission ofPDCP SDUs; ciphering, deciphering and integrity protection; PDCP SDUdiscard; PDCP re-establishment and data recovery for RLC AM; PDCP statusreporting for RLC AM; duplication of PDCP PDUs and duplicate discardindication to lower layers. The main services and functions of the PDCPsublayer for the control plane include: sequence numbering; ciphering,deciphering and integrity protection; transfer of control plane data;reordering and duplicate detection; in-order delivery; duplication ofPDCP PDUs and duplicate discard indication to lower layers.

In the 3GPP NR system, the main services and functions of SDAP include:mapping between a QoS flow and a data radio bearer; marking QoS flow ID(QFI) in both DL and UL packets. A single protocol entity of SDAP isconfigured for each individual PDU session.

In the 3GPP NR system, the main services and functions of the RRCsublayer include: broadcast of system information related to AS and NAS;paging initiated by 5GC or NG-RAN; establishment, maintenance andrelease of an RRC connection between the UE and NG-RAN; securityfunctions including key management; establishment, configuration,maintenance and release of signaling radio bearers (SRBs) and data radiobearers (DRBs); mobility functions (including: handover and contexttransfer, UE cell selection and reselection and control of cellselection and reselection, inter-RAT mobility); QoS managementfunctions; UE measurement reporting and control of the reporting;detection of and recovery from radio link failure; NAS message transferto/from NAS from/to UE.

FIG. 8 shows a frame structure in a 3GPP based wireless communicationsystem to which implementations of the present disclosure is applied.

The frame structure shown in FIG. 8 is purely exemplary and the numberof subframes, the number of slots, and/or the number of symbols in aframe may be variously changed. In the 3GPP based wireless communicationsystem. OFDM numerologies (e.g., subcarrier spacing (SCS), transmissiontime interval (TTI) duration) may be differently configured between aplurality of cells aggregated for one UE. For example, if a UE isconfigured with different SCSs for cells aggregated for the cell, an(absolute time) duration of a time resource (e.g., a subframe, a slot,or a TTI) including the same number of symbols may be different amongthe aggregated cells. Herein, symbols may include OFDM symbols (orCP-OFDM symbols), SC-FDMA symbols (or discrete Fouriertransform-spread-OFDM (DFT-s-OFDM) symbols).

Referring to FIG. 8 , downlink and uplink transmissions are organizedinto frames. Each frame has T_(f)=10 ms duration. Each frame is dividedinto two half-frames, where each of the half-frames has 5 ms duration.Each half-frame consists of 5 subframes, where the duration T f persubframe is 1 ms. Each subframe is divided into slots and the number ofslots in a subframe depends on a subcarrier spacing. Each slot includes14 or 12 OFDM symbols based on a cyclic prefix (CP). In a normal CP,each slot includes 14 OFDM symbols and, in an extended CP, each slotincludes 12 OFDM symbols. The numerology is based on exponentiallyscalable subcarrier spacing Δf=2^(u)*15 kHz.

Table 1 shows the number of OFDM symbols per slot N^(slot) _(symb), thenumber of slots per frame N^(frame,u) _(slot), and the number of slotsper subframe N^(subframe,u) _(slot) for the normal CP, according to thesubcarrier spacing Δf=2^(u)*15 kHz.

TABLE 1 u N^(slot) _(symb) N^(frame, u) _(slot) N^(subframe, u) _(slot)0 14 10 1 1 14 20 2 2 14 40 4 3 14 80 8 4 14 160 16

Table 2 shows the number of OFDM symbols per slot N^(slot) _(symb), thenumber of slots per frame N^(frame,u) _(slot), and the number of slotsper subframe N^(subframe,u) _(slot) for the extended CP, according tothe subcarrier spacing Δf=2^(u)*15 kHz.

TABLE 2 u N^(slot) _(symb) N^(frame, u) _(slot) N^(subframe, u) _(slot)2 12 40 4

A slot includes plural symbols (e.g., 14 or 12 symbols) in the timedomain. For each numerology (e.g., subcarrier spacing) and carrier, aresource grid of N^(size,u) _(grid,x)*N^(RB) _(sc) subcarriers andN^(subframe,u) _(symb) OFDM symbols is defined, starting at commonresource block (CRB) N^(size,u) _(grid,x) indicated by higher-layersignaling (e.g., RRC signaling), where N^(size,u) _(grid,x) is thenumber of resource blocks (RBs) in the resource grid and the subscript xis DL for downlink and UL for uplink. N^(RB) _(sc) is the number ofsubcarriers per RB. In the 3GPP based wireless communication system,N^(RB) _(sc) is 12 generally. There is one resource grid for a givenantenna port p, subcarrier spacing configuration u, and transmissiondirection (DL or UL). The carrier bandwidth N^(size,u) _(grid) forsubcarrier spacing configuration u is given by the higher-layerparameter (e.g., RRC parameter). Each element in the resource grid forthe antenna port p and the subcarrier spacing configuration u isreferred to as a resource element (RE) and one complex symbol may bemapped to each RE. Each RE in the resource grid is uniquely identifiedby an index k in the frequency domain and an index l representing asymbol location relative to a reference point in the time domain. In the3GPP based wireless communication system, an RB is defined by 12consecutive subcarriers in the frequency domain. In the 3GPP NR system,RBs are classified into CRBs and physical resource blocks (PRBs). CRBsare numbered from 0 and upwards in the frequency domain for subcarrierspacing configuration u. The center of subcarrier 0 of CRB 0 forsubcarrier spacing configuration u coincides with ‘point A’ which servesas a common reference point for resource block grids. In the 3GPP NRsystem, PRBs are defined within a bandwidth part (BWP) and numbered from0 to N^(size) _(BWP,i)−1, where i is the number of the bandwidth part.The relation between the physical resource block n_(PRB) in thebandwidth part i and the common resource block n_(CRB) is as follows:n_(PRB)=n_(CRB)+N^(size) _(BWP,i), where N^(size) _(BWP,i) is the commonresource block where bandwidth part starts relative to CRB 0. The BWPincludes a plurality of consecutive RBs. A carrier may include a maximumof N (e.g., 5) BWPs. A UE may be configured with one or more BWPs on agiven component carrier. Only one BWP among BWPs configured to the UEcan active at a time. The active BWP defines the UE's operatingbandwidth within the cell's operating bandwidth.

The NR frequency band may be defined as two types of frequency range,i.e., FR1 and FR2. The numerical value of the frequency range may bechanged. For example, the frequency ranges of the two types (FR1 andFR2) may be as shown in Table 3 below. For ease of explanation, in thefrequency ranges used in the NR system, FR1 may mean “sub 6 GHz range”,FR2 may mean “above 6 GHz range,” and may be referred to as millimeterwave (mmW).

TABLE 3 Frequency Range Corresponding designation frequency rangeSubcarrier Spacing FR1  450 MHz-6000 MHz  15, 30, 60 kHz FR2 24250MHz-52600 MHz 60, 120, 240 kHz

As mentioned above, the numerical value of the frequency range of the NRsystem may be changed. For example, FR1 may include a frequency band of410 MHz to 7125 MHz as shown in Table 4 below. That is, FR1 may includea frequency band of 6 GHz (or 5850, 5900, 5925 MHz, etc.) or more. Forexample, a frequency band of 6 GHz (or 5850, 5900, 5925 MHz, etc.) ormore included in FR1 may include an unlicensed band. Unlicensed bandsmay be used for a variety of purposes, for example for communication forvehicles (e.g., autonomous driving).

TABLE 4 Frequency Range Corresponding designation frequency rangeSubcarrier Spacing FR1  410 MHz-7125 MHz  15, 30, 60 kHz FR2 24250MHz-52600 MHz 60, 120, 240 kHz

In the present disclosure, the term “cell” may refer to a geographicarea to which one or more nodes provide a communication system, or referto radio resources. A “cell” as a geographic area may be understood ascoverage within which a node can provide service using a carrier and a“cell” as radio resources (e.g., time-frequency resources) is associatedwith bandwidth which is a frequency range configured by the carrier. The“cell” associated with the radio resources is defined by a combinationof downlink resources and uplink resources, for example, a combinationof a DL component carrier (CC) and a UL CC. The cell may be configuredby downlink resources only, or may be configured by downlink resourcesand uplink resources. Since DL coverage, which is a range within whichthe node is capable of transmitting a valid signal, and UL coverage,which is a range within which the node is capable of receiving the validsignal from the UE, depends upon a carrier carrying the signal, thecoverage of the node may be associated with coverage of the “cell” ofradio resources used by the node. Accordingly, the term “cell” may beused to represent service coverage of the node sometimes, radioresources at other times, or a range that signals using the radioresources can reach with valid strength at other times. In CA, two ormore CCs are aggregated. A UE may simultaneously receive or transmit onone or multiple CCs depending on its capabilities. CA is supported forboth contiguous and non-contiguous CCs. When CA is configured, the UEonly has one RRC connection with the network. At RRC connectionestablishment/re-establishment/handover, one serving cell provides theNAS mobility information, and at RRC connectionre-establishment/handover, one serving cell provides the security input.This cell is referred to as the primary cell (PCell). The PCell is acell, operating on the primary frequency, in which the UE eitherperforms the initial connection establishment procedure or initiates theconnection re-establishment procedure. Depending on UE capabilities,secondary cells (SCells) can be configured to form together with thePCell a set of serving cells. An SCell is a cell providing additionalradio resources on top of special cell (SpCell). The configured set ofserving cells for a UE therefore always consists of one PCell and one ormore SCells. For dual connectivity (DC) operation, the term SpCellrefers to the PCell of the master cell group (MCG) or the primary SCell(PSCell) of the secondary cell group (SCG). An SpCell supports PUCCHtransmission and contention-based random access, and is alwaysactivated. The MCG is a group of serving cells associated with a masternode, comprised of the SpCell (PCell) and optionally one or more SCells.The SCG is the subset of serving cells associated with a secondary node,comprised of the PSCell and zero or more SCells, for a UE configuredwith DC. For a UE in RRC_CONNECTED not configured with CA/DC, there isonly one serving cell comprised of the PCell. For a UE in RRC_CONNECTEDconfigured with CA/DC, the term “serving cells” is used to denote theset of cells comprised of the SpCell(s) and all SCells. In DC, two MACentities are configured in a UE: one for the MCG and one for the SCG.

FIG. 9 shows a data flow example in the 3GPP NR system to whichimplementations of the present disclosure is applied.

Referring to FIG. 9 , “RB” denotes a radio bearer, and “H” denotes aheader. Radio bearers are categorized into two groups: DRBs for userplane data and SRBs for control plane data. The MAC PDU istransmitted/received using radio resources through the PHY layer to/froman external device. The MAC PDU arrives to the PHY layer in the form ofa transport block.

In the PHY layer, the uplink transport channels UL-SCH and RACH aremapped to their physical channels PUSCH and PRACH, respectively, and thedownlink transport channels DL-SCH, BCH and PCH are mapped to PDSCH,PBCH and PDSCH, respectively. In the PHY layer, uplink controlinformation (UCI) is mapped to PUCCH, and downlink control information(DCI) is mapped to PDCCH. A MAC PDU related to UL-SCH is transmitted bya UE via a PUSCH based on an UL grant, and a MAC PDU related to DL-SCHis transmitted by a BS via a PDSCH based on a DL assignment.

Support for vehicle-to-vehicle (V2V) and vehicle-to-everything (V2X)services has been introduced in LTE during Releases 14 and 15, in orderto expand the 3GPP platform to the automotive industry. These work itemsdefined an LTE sidelink suitable for vehicular applications, andcomplementary enhancements to the cellular infrastructure.

Further to this work, requirements for support of enhanced V2X use caseshave been defined in 5G LTE/NR, which are broadly arranged into four usecase groups:

1) Vehicles platooning enables the vehicles to dynamically form aplatoon travelling together. All the vehicles in the platoon obtaininformation from the leading vehicle to manage this platoon. Theseinformation allow the vehicles to drive closer than normal in acoordinated manner, going to the same direction and travelling together.

2) Extended Sensors enables the exchange of raw or processed datagathered through local sensors or live video images among vehicles, roadsite units, devices of pedestrian and V2X application servers. Thevehicles can increase the perception of their environment beyond of whattheir own sensors can detect and have a more broad and holistic view ofthe local situation. High data rate is one of the key characteristics.

3) Advanced driving enables semi-automated or full-automated driving.Each vehicle and/or RSU shares its own perception data obtained from itslocal sensors with vehicles in proximity and that allows vehicles tosynchronize and coordinate their trajectories or maneuvers. Each vehicleshares its driving intention with vehicles in proximity too.

4) Remote driving enables a remote driver or a V2X application tooperate a remote vehicle for those passengers who cannot drive bythemselves or remote vehicles located in dangerous environments. For acase where variation is limited and routes are predictable, such aspublic transportation, driving based on cloud computing can be used.High reliability and low latency are the main requirements.

NR sidelink (SL) unicast, groupcast, and broadcast design is described.SL broadcast, groupcast, and unicast transmissions are supported for thein-coverage, out-of-coverage and partial-coverage scenarios.

FIGS. 10 and 11 show an example of PC5 protocol stacks to whichimplementations of the present disclosure is applied.

FIG. 10 illustrates an example of a PC5 control plane (PC5-C) protocolstack between UEs. The AS protocol stack for the control plane in thePC5 interface consists of at least RRC, PDCP, RLC and MAC sublayers, andthe physical layer.

FIG. 11 illustrates an example of a PC5 user plane (PC5-U) protocolstack between UEs. The AS protocol stack for user plane in the PC5interface consists of at least PDCP, RLC and MAC sublayers, and thephysical layer.

For the purposes of physical layer analysis, it is assumed that higherlayers decide if unicast, groupcast, or broadcast transmission is to beused for a particular data transfer, and they correspondingly inform thephysical layer. When considering a unicast or groupcast transmission, itis assumed that the UE is able to establish which unicast or groupcastsession a transmission belongs to, and that the following identities isknown to the physical layer:

-   -   The layer-1 destination ID, conveyed via physical sidelink        control channel (PSCCH)    -   Additional layer-1 ID(s), conveyed via PSCCH, at least for the        purpose of identifying which transmissions can be combined in        reception when HARQ feedback is in use    -   HARQ process ID

For the purpose of Layer 2 analysis, it is assumed that upper layers(i.e., above AS) provide the information on whether it is a unicast,groupcast or broadcast transmission for a particular data transfer. Forthe unicast and groupcast transmission in SL, the following identitiesis known to Layer 2:

-   -   Unicast: destination ID, source ID    -   Groupcast: destination group ID, source ID

Discovery procedure and related messages for the unicast and groupcasttransmission are up to upper layers.

At least the following two SL resource allocation modes are defined asfollows.

(1) Mode 1: BS schedules SL resource(s) to be used by UE for SLtransmission(s).

(2) Mode 2: UE determines, i.e., BS does not schedule, SL transmissionresource(s) within SL resources configured by BS/network orpre-configured SL resources.

The definition of SL resource allocation Mode 2 covers:

a) UE autonomously selects SL resource for transmission

b) UE assists SL resource selection for other UE(s)

c) UE is configured with NR configured grant (Type-1 like) for SLtransmission

d) UE schedules SL transmissions of other UEs

For SL resource allocation Mode 2, sensing and resource(re-)selection-related procedures may be considered. The sensingprocedure considered is defined as decoding sidelink control information(SCI) from other UEs and/or SL measurements. The resource (re-)selectionprocedure considered uses the results of the sensing procedure todetermine resource(s) for SL transmission.

For Mode 2(a), SL sensing and resource selection procedures may beconsidered in the context of a semi-persistent scheme where resource(s)are selected for multiple transmissions of different TBs and a dynamicscheme where resource(s) are selected for each TB transmission.

The following techniques may be considered to identify occupied SLresources:

-   -   Decoding of SL control channel transmissions    -   SL measurements    -   Detection of SL transmissions

The following aspects may be considered for SL resource selection:

-   -   How a UE selects resource for PSCCH and physical sidelink shared        channel (PSSCH) transmission (and other SL physical        channel/signals that are defined)    -   Which information is used by UE for resource selection procedure

Mode 2(b) is a functionality that can be part of Mode 2(a), (c), (d)operation.

For out-of-coverage operation, Mode 2(c) assumes a (pre-)configurationof single or multiple SL transmission patterns, defined on each SLresource pool. For in-coverage operation, Mode 2(c) assumes that gNBconfiguration indicates single or multiple SL transmission patterns,defined on each SL resource pool. If there is a single patternconfigured to a transmitting UE, there is no sensing procedure executedby UE, while if multiple patterns are configured, there is a possibilityof a sensing procedure.

A pattern is defined by the size and position(s) of the resource in timeand frequency, and the number of resources.

For Mode 2(d), the procedures to become or serve as a scheduling UE forin-coverage and out-of-coverage scenarios may be considered as follows:

-   -   Scheduling UE is configured by gNB    -   Application layer or pre-configuration selects scheduling UE    -   Receiver UE schedules transmissions of the transmitter UE during        the session    -   Scheduling UE is decided by multiple UEs including the one that        is finally selected. The UE may autonomously decide to serve as        a scheduling UE/offer scheduling UE functions (i.e., by        self-nomination).

Until Rel-15, broadcast transmission is supported only for V2Xcommunication. Broadcast transmission means that V2X transmission by onewireless device is broadcast to several unspecified wireless devices. Incase of NR V2X, unicast and groupcast transmission may also be supportedfor V2X communication as well as broadcast transmission. Unicasttransmission means that V2X transmission by one wireless device istransmitted to one specified other wireless device. Groupcasttransmission means that V2X transmission by one wireless device istransmitted to several specified other wireless devices which belongs toa group. Unicast transmission is expected to be used for highreliability and low latency cases, e.g., extended sensor sharing andremote driving, emergency, etc.

In NR V2X, one wireless device may establish a PC5 link (e.g.,one-to-one connection and/or session between wireless devices) forunicast service with another wireless device. PC5 Signaling protocolabove RRC layer in the wireless devices may be used for unicast linkestablishment and management. Based on the unicast link establishmentand management, the wireless devices may exchange PC5 signaling (i.e.,upper layer signaling than RRC signaling) to successfully orunsuccessfully establish a unicast link with security activation orrelease the established unicast link.

Hereinafter, Sidelink HARQ operation is described. It may be referred toas Section 5.14.1.2 of 3GPP TS 36.321 v15.7.0.

Sidelink HARQ Entity is described.

The MAC entity is configured by upper layers to transmit using pool(s)of resources on one or multiple carriers. For each carrier, there is oneSidelink HARQ Entity at the MAC entity for transmission on SL-SCH, whichmaintains a number of parallel Sidelink processes.

For V2X sidelink communication, the maximum number of transmittingSidelink processes associated with each Sidelink HARQ Entity is 8. Asidelink process may be configured for transmissions of multiple MACPDUs. For transmissions of multiple MAC PDUs, the maximum number oftransmitting Sidelink processes associated with each Sidelink HARQEntity is 2.

A delivered and configured sidelink grant and its associated HARQinformation are associated with a Sidelink process.

For each subframe of the SL-SCH and each Sidelink process, the SidelinkHARQ Entity shall:

-   -   if a sidelink grant corresponding to a new transmission        opportunity has been indicated for this Sidelink process and        there is SL data, for sidelink logical channels of ProSe        destination associated with this sidelink grant, available for        transmission:    -   obtain the MAC PDU from the “Multiplexing and assembly” entity;    -   deliver the MAC PDU and the sidelink grant and the HARQ        information to this Sidelink process;    -   instruct this Sidelink process to trigger a new transmission.    -   else, if this subframe corresponds to retransmission opportunity        for this Sidelink process:    -   instruct this Sidelink process to trigger a retransmission.

Sidelink process is described.

The Sidelink process is associated with a HARQ buffer.

The sequence of redundancy versions is 0, 2, 3, 1. The variableCURRENT_IRV is an index into the sequence of redundancy versions. Thisvariable is updated modulo 4.

New transmissions and retransmissions either for a given SC period insidelink communication or in V2X sidelink communication are performed onthe resource indicated in the sidelink grant and with the MCS selected.

If the sidelink process is configured to perform transmissions ofmultiple MAC PDUs for V2X sidelink communication the process maintains acounter SL_RESOURCE_RESELECTION_COUNTER. For other configurations of thesidelink process, this counter is not available.

If the Sidelink HARQ Entity requests anew transmission, the Sidelinkprocess shall:

-   -   set CURRENT_IRV to 0;    -   store the MAC PDU in the associated HARQ buffer;    -   store the sidelink grant received from the Sidelink HARQ Entity;    -   generate a transmission as described below.

If the Sidelink HARQ Entity requests a retransmission, the Sidelinkprocess shall:

-   -   generate a transmission as described below.

To generate a transmission, the Sidelink process shall:

-   -   if there is no uplink transmission; or if the MAC entity is able        to perform uplink transmissions and transmissions on SL-SCH        simultaneously at the time of the transmission; or if there is a        MAC PDU to be transmitted in this TTI in uplink, except a MAC        PDU obtained from the Msg3 buffer and transmission of V2X        sidelink communication is prioritized over uplink transmission;        and    -   if there is no Sidelink Discovery Gap for Transmission or no        transmission on PSDCH at the time of the transmission; or, in        case of transmissions of V2X sidelink communication, if the MAC        entity is able to perform transmissions on SL-SCH and        transmissions on PSDCH simultaneously at the time of the        transmission:    -   instruct the physical layer to generate a transmission according        to the stored sidelink grant with the redundancy version        corresponding to the CURRENT_IRV value.    -   increment CURRENT_IRV by 1;    -   if this transmission corresponds to the last transmission of the        MAC PDU:    -   decrement SL_RESOURCE_RESELECTION_COUNTER by 1, if available.

The transmission of the MAC PDU for V2X sidelink communication isprioritized over uplink transmissions if the following conditions aremet:

-   -   if the MAC entity is not able to perform all uplink        transmissions and all transmissions of V2X sidelink        communication simultaneously at the time of the transmission;        and    -   if uplink transmission is not prioritized by upper layer: and    -   if the value of the highest priority of the sidelink logical        channel(s) in the MAC PDU is lower than thresSL-TxPrioriization        if thresSL-TxPrioritizaion is configured.

Hereinafter, Random Access Channel (RACH) procedure in NR is described.

For NR, RACH can be configured either 2-step RACH or 4-step RACH.

For 4-step RACH, UE transmits a RACH preamble, receives Random AccessResponse MAC CE, transmits a message 3 on PUSCH, and receive ContentionResolution MAC CE.

For 2-step RACH, UE transmits a message A consisting of a RACH preambleand PUSCH resource, and receives a message B consisting of Random AccessResponse and Contention Resolution.

Meanwhile, UE may establish a unicast link and the associated PC5-RRCconnection with other UE in sidelink.

In this case. UE may monitor the quality of the PC5-RRC connection basedon HARQ retransmissions. In this case, it is unclear how the UE declareslink failure on the PC5-RRC connection.

Therefore, studies for indicating sidelink radio link failure in awireless communication system are required.

Hereinafter, a method and apparatus for indicating sidelink radio linkfailure in a wireless communication system, according to someembodiments of the present disclosure, will be described with referenceto the following drawings.

The following drawings are created to explain specific embodiments ofthe present disclosure. The names of the specific devices or the namesof the specific signals/messages/fields shown in the drawings areprovided by way of example, and thus the technical features of thepresent disclosure are not limited to the specific names used in thefollowing drawings. Herein, a wireless device may be referred to as auser equipment (UE).

FIG. 12 shows an example of a method for indicating sidelink radio linkfailure in a wireless communication system, according to someembodiments of the present disclosure.

In particular, FIG. 12 shows an example of a method performed by awireless device.

In step 1201, a first wireless device may configure a maximum number ofa counter for a PC5-Radio Resource Control (RRC) connection with asecond wireless device.

For example, a first wireless device may establish a PC5-S unicast linkand the associated PC5-RRC connection with the second wireless device.

For example, the network may send RRC Reconfiguration message to thefirst wireless device. The RRC Reconfiguration message may include themaximum number of the counter for the PC5-RRC connection with the secondwireless device.

For other example, the first wireless device may configure the maximumnumber of the counter for the PC5-RRC connection with the secondwireless device, by itself.

For example, the first wireless device may configure the counter foreach of multiple PC5-RRC connections with other wireless devices.

In step 1202, a first wireless device may initialize the counter to zeroupon 1) establishing the PC5-RRC connection with the second wirelessdevice, or 2) configuring or reconfiguring the maximum number of thecounter.

According to some embodiments of the present disclosure, the firstwireless device may configure another counter for another PC5-RRCconnection with a third wireless device.

In this case, the first wireless device may initialize the other counterto zero upon 1) establishing the other PC5-RRC connection with the thirdwireless device, or 2) configuring or reconfiguring a maximum number ofthe other counter for the other PC5-RRC connection with the thirdwireless device.

For example, a maximum number of the other counter for the other PC5-RRCconnection with the third wireless device may be same as the maximumnumber of the counter for the PC5-RRC connection with the secondwireless device.

For example, the maximum number of the counter for the PC5-RRCconnection with the second wireless device and the maximum number of theother counter for the PC5-RRC connection with the third wireless devicecould be configured or reconfigured simultaneously.

For other example, a maximum number of the other counter for the otherPC5-RRC connection with the third wireless device could be differentfrom the maximum number of the counter for the PC5-RRC connection withthe second wireless device.

For example, the maximum number of the counter for the PC5-RRCconnection with the second wireless device and the maximum number of theother counter for the PC5-RRC connection with the third wireless devicecould be configured or reconfigured independently.

In step 1203, a first wireless device may perform a transmission of aMedium Access Control (MAC) Protocol Data Unit (PDU) to the secondwireless device based on the established PC5-RRC connection.

For example, the transmission of the MAC PDU may include a PSSCHtransmission for a pair of source layer-2 ID of the first wirelessdevice and destination layer 2-ID of the second wireless devicecorresponding to the PC5-RRC connection.

For example, PSSCH may carry data from a UE for sidelink communicationand V2X sidelink communication.

For example, PSCCH may be mapped to the sidelink control resources. Forexample, PSCCH may indicate resource and other transmission parametersused by a UE for PSSCH. For V2X sidelink communication, PSCCH and PSSCHcould be transmitted in the same subframe.

In step 1204, a first wireless device may increase the counter based onno reception of any acknowledgement to the transmission of the MAC PDU.

For example, a first wireless device may monitor each Physical SidelinkFeedback Channel (PSFCH) reception occasion associated to thetransmission of the MAC PDU. Based on that PSFCH reception is absent onthe PSFCH reception occasion, the first wireless device may incrementthe counter.

According to some embodiments of the present disclosure, a firstwireless device may re-initialize the counter to zero based on receptionof any acknowledgement to the transmission of the MAC PUD.

For example, a first wireless device may monitor each PSFCH receptionoccasion associated to the transmission of the MAC PDU. Based on thatPSFCH reception is not absent on the PSFCH reception occasion, the firstwireless device may re-initialize the counter to zero.

According to some embodiments of the present disclosure, a firstwireless device may configure an N value for re-initializing the counterto zero.

For example, the N value is a natural number. For example, the N valuecould be one.

For example, the first wireless device may re-initialize the counter tozero if N acknowledgements have been received on PSFCH eitherconsecutively or in an interval.

For example, the N acknowledgements may correspond to only positiveacknowledgements successfully received on PSFCH.

For example, the N acknowledgements may correspond to only negativeacknowledgements successfully received on PSFCH.

For example, the N acknowledgements may correspond to both positive andnegative acknowledgements successfully received on PSFCH.

For example, the N acknowledgements may not include unsuccessfulreception of any acknowledgement on PSFCH.

In step 1205, a first wireless device may indicates Sidelink (SL) RadioLink Failure (RLF) for the PC5-RRC connection based on that the counterreaches the maximum number of the counter.

According to some embodiments of the present disclosure, a firstwireless device may indicate the SL RLF for the PC5-RRC connection byinforming the SL RLF to the network.

According to some embodiments of the present disclosure, a SL Hybridautomatic repeat request (HARQ) entity of a first wireless device mayindicate the SL RLF for the PC5-RRC connection to an RRC entity of thefirst wireless device.

According to some embodiments of the present disclosure, a firstwireless device may be in communication with at least one of a userequipment, a network, or an autonomous vehicle other than the firstwireless device.

FIG. 13 shows an example of a method for performing data transmission bya UE in a wireless communication system, according to some embodimentsof the present disclosure.

In step 1301, UE may establish a unicast link and the associated PC5-RRCconnection with a peer UE in sidelink.

In step 1302, UE may determine the maximum numbers of HARQ transmissionsfor declaration of the PC5-RRC connection failure.

For example, the maximum numbers of HARQ transmissions for declarationof the PC5-RRC connection failure may be configured by the network orthe peer UE.

For other example, UE may determine the maximum numbers of HARQtransmissions for declaration of the PC5-RRC connection failure based onthe QoS parameters of logical channels belonging to the PC5-RRCconnection or the unicast link.

In step 1303, UE may increase a counter when one of the followingconditions is met:

-   -   if no acknowledgement to a transmission of any MAC PDU (e.g.        HARQ feedback) has been received; and/or    -   if a negative acknowledgement to a transmission of any MAC PDU        has been received.

In step 1304, UE may reset a counter to an initial value (e.g. zero)when one of the following conditions is met:

-   -   if a parameter related to establishment of a PC5-RRC connection        or PC5-S unicast link is indicated by upper layers: and/or    -   if a very first new transmission is triggered by this sidelink        HARQ entity for the PC5-RRC connection; and/or    -   if N acknowledgements (for example, HARQ feedbacks) have been        received either consecutively or within an interval.

FIG. 14 shows an example of method for sidelink HARQ transmissions andfailure detection from a UE in a wireless communication system,according to some embodiments of the present disclosure.

In particular FIG. 14 shows an example of sidelink HARQ transmissionsand failure detection from a UE according to the present disclosure.However, it is clear that present disclosure is not limited thereto. Thepresent disclosure could be applied to quality reporting for uplink datatransmission as well.

In step 1401, TX UE may establish a PC5-S unicast link and theassociated PC5-RRC connection with RX UE.

In step 1402, TX UE may send Sidelink UE information indicating thedestination ID of the RX UE to the network. TX UE may indicate thedestination ID and the associated QoS information to the network via theSidelink UE Information. The destination ID may be associated to adestination index according to the contents of the Sidelink UEInformation.

In step 1403, upon receiving the Sidelink UE information, the networkmay send RRC Reconfiguration message to the TX UE. The message mayinclude N value and maxHARQRetxThreshold with the destination index.

In TX UE, the Sidelink HARQ Entity may maintain an N value,maxHARQRetxThreshold and MAX_RLM_ReTX_COUNT for each PC5-RRC connectionthat has established by RRC (or for each PC5-S unicast link establishedby PC5-S entity, each destination or each pair of a Source Layer-2 IDand a Destination Layer-2 ID).

The N value and maxHARQRetxThreshold may be configured by RRC for thePC5-RRC connection (or the PC5-S unicast link established by PC5-Sentity, the destination or the pair of a Source Layer-2 ID and aDestination Layer-2 ID).

The Sidelink HARQ Entity may correspond both receiving and transmittingSidelink HARQ Entity or either receiving or transmitting Sidelink HARQEntity.

The maxHARQRetxThreshold may be configured with the value of themaxHARQRetxThreshold configured for the logical channel with the highestpriority belonging to the PC5-RRC connection or with the lowest, anaverage or highest value of all maxHARQRetxThreshold values configuredfor all logical channels belonging to the PC5-RRC connection (or thePC5-S unicast link established by PC5-S entity, the destination or thepair of a Source Layer-2 ID and a Destination Layer-2 ID).

The N value may be configured with the value of the N value configuredfor the logical channel with the highest priority belonging to thePC5-RRC connection or with the lowest, an average or highest value ofall N values configured for all logical channels belonging to thePC5-RRC connection (or the PC5-S unicast link established by PC5-Sentity, the destination or the pair of a Source Layer-2 ID and aDestination Layer-2 ID).

The Sidelink HARQ Entity in TX UE may set the MAX_RLM_ReTX_COUNT to zerofor each PC5-RRC connection that has established by RRC (or for eachPC5-S unicast link established by PC5-S entity, each destination or eachpair of a Source Layer-2 ID and a Destination Layer-2 ID), when one ofthe following conditions is met:

-   -   if max-HARQRetxThreshold is configured by RRC (for example,        initial step of HARQ based RLM e.g. upon establishment of a        PC5-RRC connection or PC5-S unicast link); and/or    -   if a parameter related to establishment of a PC5-RRC connection        or PC5-S unicast link is indicated by upper layers; and/or    -   if a very first new transmission is triggered by this sidelink        HARQ entity for the PC5-RRC connection (or the PC5-S unicast        link established by PC5-S entity, the destination or the pair of        a Source Layer-2 ID and a Destination Layer-2 ID): and/or    -   if N acknowledgements have been received on PSFCH either        consecutively or in an interval (Wherein N can be one or more):        -   The N acknowledgements may correspond to only positive            acknowledgements successfully received on PSFCH; and/or        -   The N acknowledgements may correspond to only negative            acknowledgements successfully received on PSFCH; and/or        -   The N acknowledgements may correspond to both positive and            negative acknowledgements successfully received on PSFCH;            and/or        -   The N acknowledgements may not include unsuccessful            reception of any acknowledgement on PSFCH (for example,            either no HARQ feedback transmission of an acknowledgement            from a peer UE (for example, because the peer UE does not            successfully receive the corresponding PSCCH and/or PSSCH)            or no reception of HARQ feedback transmission from a peer UE            (for example, because this UE does not successfully receive            the corresponding PSFCH).

In step 1404, the Sidelink HARQ Entity in TX UE may increment theMAX_RLM_ReTX_COUNT for each PC5-RRC connection that has established byRRC (or for each PC5-S unicast link established by PC5-S entity, eachdestination or each pair of a Source Layer-2 ID and a DestinationLayer-2 ID), when one of the following conditions is met:

-   -   if no acknowledgement to a transmission of any MAC PDU has been        received on PSFCH; and/or        -   Option 1: the acknowledgement may only correspond to a            positive acknowledgement successfully received on PSFCH;        -   Option 2: the acknowledgement may only correspond to a            negative acknowledgement successfully received on PSFCH;        -   Option 3: the acknowledgement may only correspond to either            a positive or a negative acknowledgement successfully            received on PSFCH;    -   if a negative acknowledgement to a transmission of any MAC PDU        has been received on PSFCH.

For example, in step 1404 a, TX UE may transmit a MAC PDU to RX UE. Instep 1404 b, TX UE may receive the NACK from RX UE. In step 1404 c,based on receiving the NACK related to the MAC PDU, TX UE may incrementthe MAX_RLM_ReTX_Count.

For example, in step 1404 d, TX UE may transmit a MAC PDU to RX UE. Instep 1404 e, based on no reception of any acknowledgement (ACK or NACK)related to the MAC PDU, TX UE may increment the MAX_RLM_ReTX_Count.

For example, in step 1404 f, TX UE may transmit a MAC PDU to RX UE. Instep 1404 g, TX UE may receive an ACK from RX UE. In step 1404 h, TX UEmay transmit a MAC PDU to RX UE. In step 1404 i, TX UE may receive anACK from RX UE. In step 1404 j, based on that TX UE receives twoconsecutive ACK from RX UE (for example, the N value may be configuredas two), the TX UE may reset the MAX_RLM_ReTX_Count.

For example, in step 1404 k, TX UE may transmit a MAC PDU to RX UE. Instep 1404 l, based on no reception of any acknowledgement (ACK or NACK)related to the MAC PDU, TX UE may increment the MAX_RLM_ReTX_Count. Instep 1404 m, TX UE may transmit a MAC PDU to RX UE. In step 1404 n,based on no reception of any acknowledgement related to the MAC PDU, TXUE may increment the MAX_RLM_ReTX_Count. In step 1404 o, TX UE maytransmit a MAC PDU to RX UE. In step 1404 p, based on no reception ofany acknowledgement related to the MAC PDU, TX UE may increment theMAX_RLM_ReTX_Count.

In step 1405, if MAX_RLM_ReTX_COUNT reaches maxHARQRetxThreshold, theMAC entity in TX UE may indicate to RRC that max HARQ retransmission hasbeen reached for each PC5-RRC connection that has established by RRC (orfor each PC5-S unicast link established by PC5-S entity, eachdestination or each pair of a Source Layer-2 ID and a DestinationLayer-2 ID)

In step 1406, upon receiving this indication from the MAC entity, TX UERRC may declare sidelink radio link failure on the corresponding PC5-RRCconnection (or the corresponding pair or the corresponding destination)and indicate sidelink radio link failure to the network.

According to some embodiments of the present disclosure, the ULtransmissions and SL transmissions could be performed for different RATsor the same RAT.

The present disclosure could be also applied to radio link failure ofdifferent uplink transmissions to different base stations, for example,configured for dual connectivity or carrier aggregation in uplink. Inthis case, the TX UE in FIG. 14 can be replaced by the same or adifferent base station.

Hereinafter, a method for indicating sidelink radio link failure in awireless communication system, according to some embodiments of thepresent disclosure will be described. The method may be performed by awireless device, for example, a UE.

According to some embodiments of the present disclosure, a UE mayperform Sidelink HARQ operation.

For example, a sidelink HARQ Entity of a UE may perform the followingoperations.

The MAC entity includes at most one Sidelink HARQ entity fortransmission on SL-SCH, which maintains a number of parallel Sidelinkprocesses.

The maximum number of transmitting Sidelink processes associated withthe Sidelink HARQ Entity is [TBD]. [A sidelink process may be configuredfor transmissions of multiple MAC PDUs. For transmissions of multipleMAC PDUs, the maximum number of transmitting Sidelink processesassociated with the Sidelink HARQ Entity is [TBD].]

A delivered sidelink grant and its associated HARQ information areassociated with a Sidelink process. Each Sidelink process supports oneTB.

For each sidelink grant, the Sidelink HARQ Entity shall:

1> associate a Sidelink process to this grant, and for each associatedSidelink process:

2> if the MAC entity determines that the sidelink grant is used forinitial transmission, and if no MAC PDU has been obtained:

For the configured grant Type 1 and 2, whether a sidelink grant is usedfor initial transmission or retransmission is up to UE implementation.

3> obtain the MAC PDU to transmit from the Multiplexing and assemblyentity, if any;

3> if a MAC PDU to transmit has been obtained:

4> deliver the MAC PDU, the sidelink grant and the HARQ information andthe QoS information of the TB to the associated Sidelink process;

4> instruct the associated Sidelink process to trigger a newtransmission;

3> else:

4> flush the HARQ buffer of the associated Sidelink process.

2> else (i.e. retransmission):

3> if a positive acknowledgement to a transmission of the MAC PDU hasbeen received, or

3> if only a negative acknowledgement is configured and no negativeacknowledgement is for the most recent (re-)transmission of the MAC PDU:

4> clear the sidelink grant;

4> flush the HARQ buffer of the associated Sidelink process;

3> else:

4> deliver the sidelink grant and HARQ information and QoS informationof the MAC PDU to the associated Sidelink process:

4> instruct the associated Sidelink process to trigger a retransmission.

The Sidelink HARQ Entity maintains an N value, maxHARQRetxThreshold andMAX_RLM_ReTX_COUNT only for unicast in sidelink for each PC5-RRCconnection that has established by RRC (or for each PC5-S unicast linkestablished by PC5-S entity, each destination or each pair of a SourceLayer-2 ID and a Destination Layer-2 ID). The N value andmaxHARQRetxThreshold are configured by RRC for the PC5-RRC connection(or the PC5-S unicast link established by PC5-S entity, the destinationor the pair of a Source Layer-2 ID and a Destination Layer-2 ID).

Wherein the Sidelink HARQ Entity corresponds both receiving andtransmitting Sidelink HARQ Entity or either receiving or transmittingSidelink HARQ Entity.

Alternatively, the maxHARQRetxThreshold is configured with the value ofthe maxHARRetxThreshold configured for the logical channel with thehighest priority belonging to the PC5-RRC connection or with the lowest,an average or highest value of all maxHARQRetxThreshold valuesconfigured for all logical channels belonging to the PC5-RRC connection(or the PC5-S unicast link established by PC5-S entity, the destinationor the pair of a Source Layer-2 ID and a Destination Layer-2 ID).

Alternatively, the N value is configured with the value of the N valueconfigured for the logical channel with the highest priority belongingto the PC5-RRC connection or with the lowest, an average or highestvalue of all N values configured for all logical channels belonging tothe PC5-RRC connection (or the PC5-S unicast link established by PC5-Sentity, the destination or the pair of a Source Layer-2 ID and aDestination Layer-2 ID).

The Sidelink HARQ Entity shall for each PC5-RRC connection that hasestablished by RRC (or for each PC5-S unicast link established by PC5-Sentity, each destination or each pair of a Source Layer-2 ID and aDestination Layer-2 ID):

1> if maxHARQRetxThreshold is configured by RRC (i.e. initial step ofHARQ based RLM e.g. upon establishment of a PC5-RRC connection or PC5-Sunicast link); or

1> if a parameter related to establishment of a PC5-RRC connection orPC5-S unicast link is indicated by upper layers: or

1> if a very first new transmission is triggered by this sidelink HARQentity for the PC5-RRC connection (or the PC5-S unicast link establishedby PC5-S entity, the destination or the pair of a Source Layer-2 ID anda Destination Layer-2 ID); or

1> if N acknowledgements have been received on PSFCH eitherconsecutively or in an interval; or

Option 1: the N acknowledgements correspond to only positiveacknowledgements successfully received on PSFCH;

Option 2: the N acknowledgements correspond to only negativeacknowledgements successfully received on PSFCH;

Option 3: the N acknowledgements correspond to both positive andnegative acknowledgements successfully received on PSFCH;

Wherein the N acknowledgements do not include unsuccessful reception ofany acknowledgement on PSFCH (i.e. either no HARQ feedback transmissionof an acknowledgement from a peer UE (e.g. because the peer UE does notsuccessfully receive the corresponding PSCCH and/or PSSCH) or noreception of HARQ feedback transmission from a peer UE (e.g. becausethis UE does not successfully receive the corresponding PSFCH). WhereinN can be one or more.

2> set the MAX_RLM_ReTX_COUNT to zero.

1> if no acknowledgement to a transmission of any MAC PDU has beenreceived on PSFCH; or

Option 1: the acknowledgement only corresponds to a positiveacknowledgement successfully received on PSFCH:

Option 2: the acknowledgement only corresponds to a negativeacknowledgement successfully received on PSFCH:

Option 3: the acknowledgement only corresponds to either a positive or anegative acknowledgement successfully received on PSFCH;

1> if a negative acknowledgement to a transmission of any MAC PDU hasbeen received on PSFCH:

2> increment the MAX_RLM_ReTX_COUNT.

1> if MAX_RLM_ReTX_COUNT=maxHARQRetxThreshold:

-   -   indicate to RRC that max HARQ retransmission has been reached.

Upon receiving this indication from the MAC entity. UE RRC declaressidelink radio link failure on the corresponding PC5-RRC connection (orthe corresponding pair or the corresponding destination).

Hereinafter, a method for indicating sidelink radio link failure in awireless communication system, according to some embodiments of thepresent disclosure will be described. The method may be performed by awireless device, for example, a UE.

According to some embodiments of the present disclosure, a UE mayperform Sidelink HARQ operation.

For example, a sidelink HARQ Entity of a UE may perform the followingoperations.

The MAC entity includes at most one Sidelink HARQ entity fortransmission on SL-SCH, which maintains a number of parallel Sidelinkprocesses.

There is at most one Sidelink HARQ Entity at the MAC entity forreception of the SL-SCH, which maintains a number of parallel Sidelinkprocesses.

Each Sidelink process is associated with SCI in which the MAC entity isinterested. This interest is as determined by the Destination Layer-1 IDand the Source Layer-1 ID of the SCI. The Sidelink HARQ Entity directsHARQ information and associated TBs received on the SL-SCH to thecorresponding Sidelink processes.

The number of Receiving Sidelink processes associated with the SidelinkHARQ Entity is defined in [TBD].

For each PSSCH duration, the Sidelink HARQ Entity shall:

1> for each SCI valid for this PSSCH duration:

2> if this PSSCH duration corresponds to new transmission opportunityaccording to this SCI:

3> allocate the TB received from the physical layer and the associatedHARQ information to an unoccupied Sidelink process, associate theSidelink process with this SCI and consider this transmission to be anew transmission.

1> for each Sidelink process:

2> if this PSSCH duration corresponds to retransmission opportunity forthe Sidelink process according to its associated SCI:

3> allocate the TB received from the physical layer and the associatedHARQ information to the Sidelink process and consider this transmissionto be a retransmission.

The Sidelink HARQ Entity maintains an N value, maxHARQRetxThreshold andMAX_RLM_ReTX_COUNT only for unicast in sidelink for each PC5-RRCconnection that has established by RRC (or for each PC5-S unicast linkestablished by PC5-S entity, each destination or each pair of a SourceLayer-2 ID and a Destination Layer-2 ID). The N value andmaxHARQRetxThreshold are configured by RRC for the PC5-RRC connection(or the PC5-S unicast link established by PC5-S entity, the destinationor the pair of a Source Layer-2 ID and a Destination Layer-2 ID).

Wherein the Sidelink HARQ Entity corresponds both receiving andtransmitting Sidelink HARQ Entity or either receiving or transmittingSidelink HARQ Entity.

Alternatively, the maxHARQRetxThreshold is configured with the value ofthe maxHARQRetxThreshold configured for the logical channel with thehighest priority belonging to the PC5-RRC connection or with the lowest,an average or highest value of all maxHARQRetxThreshold valuesconfigured for all logical channels belonging to the PC5-RRC connection(or the PC5-S unicast link established by PC5-S entity, the destinationor the pair of a Source Layer-2 ID and a Destination Layer-2 ID).

Alternatively, the N value is configured with the value of the N valueconfigured for the logical channel with the highest priority belongingto the PC5-RRC connection or with the lowest, an average or highestvalue of all N values configured for all logical channels belonging tothe PC5-RRC connection (or the PC5-S unicast link established by PC5-Sentity, the destination or the pair of a Source Layer-2 ID and aDestination Layer-2 ID).

The Sidelink HARQ Entity shall for each PC5-RRC connection that hasestablished by RRC (or for each PC5-S unicast link established by PC5-Sentity, each destination or each pair of a Source Layer-2 ID and aDestination Layer-2 ID):

1> if maxHARQRetxThreshold is configured by RRC (i.e. initial step ofHARQ based RLM e.g. upon establishment of a PC5-RRC connection or PC5-Sunicast link), or

1> if a parameter related to establishment of a PC5-RRC connection orPC5-S unicast link is indicated by upper layers; or

1> if a SCI transmission scheduling a very first (re-)transmission isreceived for the PC5-RRC connection (or the PC5-S unicast linkestablished by PC5-S entity, the destination or the pair of a SourceLayer-2 ID and a Destination Layer-2 ID); or

1> if a very first (re-)transmission is received by this sidelink HARQentity for the PC5-RRC connection (or the PC5-S unicast link establishedby PC5-S entity, the destination or the pair of a Source Layer-2 ID anda Destination Layer-2 ID); or

1> if N acknowledgements have been transmitted on PSFCH eitherconsecutively or in an interval; or

Option 1: the N acknowledgements correspond to only positiveacknowledgements successfully transmitted on PSFCH;

Option 2: the N acknowledgements correspond to only negativeacknowledgements successfully transmitted on PSFCH;

Option 3: the N acknowledgements correspond to both positive andnegative acknowledgements successfully transmitted on PSFCH;

Wherein the N acknowledgements do not include unsuccessful transmissionof any acknowledgement on PSFCH i.e. no HARQ feedback transmission of anacknowledgement from this UE (e.g. because this UE does not successfullyreceive the corresponding PSCCH and/or PSSCH).

Wherein N can be one or more.

2> set the MAX_RLM_ReTX_COUNT to zero.

1> if a sidelink transmission on PSCCH and/or PSSCH previously indicatedor scheduled by any SCI has been unsuccessfully received; or

1> if a negative acknowledgement to a transmission of any MAC PDU hasbeen transmitted on PSFCH; or

1> if no acknowledgement to a transmission of any MAC PDU has beentransmitted on PSFCH:

2> increment the MAX_RLM_ReTX_COUNT.

1> if MAX_RLM_ReTX_COUNT=maxHARQRetxThreshold:

-   -   indicate to RRC that max HARQ retransmission has been reached.

Upon receiving this indication from the MAC entity, UE RRC declaressidelink radio link failure on the corresponding PC5-RRC connection (orthe corresponding pair or the corresponding destination)

Hereinafter, a method for indicating sidelink radio link failure in awireless communication system, according to some embodiments of thepresent disclosure will be described. The method may be performed by awireless device, for example, a UE.

According to some embodiments of the present disclosure, a UE mayperform HARQ-based Sidelink RLF detection.

The HARQ-based Sidelink RLF detection procedure is used to detectSidelink RLF based on a number of consecutive DTX on PSFCH receptionoccasions for a PC5-RRC connection.

RRC configures the following parameter to control HARQ-based SidelinkRLF detection:

-   -   sl-maxNumConsecutiveDTX

The following UE variable is used for HARQ-based Sidelink RLF detection.

-   -   numConsecutiveDTX, which is maintained for each PC5-RRC        connection.

The Sidelink HARQ Entity shall (re-)initialize numConsecutiveDTX to zerofor each PC5-RRC connection which has been established by upper layers,if any, upon establishment of the PC5-RRC connection or(re)configuration of sl-maxNumConsecutiveDTX.

The Sidelink HARQ Entity shall for each PSFCH reception occasionassociated to the PSSCH transmission:

1> if PSFCH reception is absent on the PSFCH reception occasion:

2> increment numConsecutiveDTX by 1;

2> if numConsecutiveDTX reaches sl-maxNumConsecutiveDTX:

3> indicate HARQ-based Sidelink RLF detection to RRC.

1> else:

2> re-initialize numConsecutiveDTX to zero.

Hereinafter, an apparatus for indicating sidelink radio link failure ina wireless communication system, according to some embodiments of thepresent disclosure, will be described. Herein, the apparatus may be awireless device (100 or 200) in FIGS. 2, 3, and 5 .

For example, a first wireless device may perform methods describedabove. The detailed description overlapping with the above-describedcontents could be simplified or omitted.

Referring to FIG. 5 , a first wireless device 100 may include aprocessor 102, a memory 104, and a transceiver 106.

According to some embodiments of the present disclosure, the processor102 may be configured to be coupled operably with the memory 104 and thetransceiver 106.

The processor 102 may be configured to configure a maximum number of acounter for a PC5-Radio Resource Control (RRC) connection with a secondwireless device. The processor 102 may be configured to initialize thecounter to zero upon 1) establishing the PC5-RRC connection with thesecond wireless device, or 2) configuring or reconfiguring the maximumnumber of the counter. The processor 102 may be configured to controlthe transceiver 106 to perform a transmission of a Medium Access Control(MAC) Protocol Data Unit (PDU) to the second wireless device based onthe established PC5-RRC connection. The processor 102 may be configuredto increase the counter based on no reception of any acknowledgement tothe transmission of the MAC PDU. The processor 102 may be configured toindicate Sidelink (SL) Radio Link Failure (RLF) for the PC5-RRCconnection based on that the counter reaches the maximum number of thecounter.

According to some embodiments of the present disclosure, the processor102 may be configured to inform the SL RLF to the network.

According to some embodiments of the present disclosure, the processor102 may be configured to control an SL Hybrid automatic repeat request(HARQ) entity of the first wireless device to inform the SL RLF to anRRC entity of the first wireless device.

According to some embodiments of the present disclosure, the processor102 may be configured to configure the counter for each of multiplePC5-RRC connections with other wireless devices.

According to some embodiments of the present disclosure, the processor102 may be configured to configure another counter for another PC5-RRCconnection with a third wireless device.

For example, the processor 102 may be configured to initialize the othercounter to zero upon 1) establishing the other PC5-RRC connection withthe third wireless device, or 2) configuring or reconfiguring a maximumnumber of the other counter for the other PC5-RRC connection with thethird wireless device.

For example, a maximum number of the other counter for the other PC5-RRCconnection with the third wireless device may be same as the maximumnumber of the counter for the PC5-RRC connection with the secondwireless device.

According to some embodiments of the present disclosure, the processor102 may be configured to monitor each Physical Sidelink Feedback Channel(PSFCH) reception occasion associated to the transmission of the MACPDU. Based on that PSFCH reception is absent on the PSFCH receptionoccasion, the processor 102 may be configured to increment the counter.

According to some embodiments of the present disclosure, the processor102 may be configured to re-initialize the counter to zero based onreception of any acknowledgement to the transmission of the MAC PUD.

For example, the processor 102 may be configured to monitor each PSFCHreception occasion associated to the transmission of the MAC PDU. Basedon that PSFCH reception is not absent on the PSFCH reception occasion,the processor 102 may be configured to re-initialize the counter tozero.

According to some embodiments of the present disclosure, thetransmission of the MAC PDU may include a PSSCH transmission for a pairof source layer-2 ID of the first wireless device and destination layer2-ID of the second wireless device corresponding to the PC5-RRCconnection.

According to some embodiments of the present disclosure, the processor102 may be configured to be in communication with at least one of a userequipment, a network, or an autonomous vehicle other than the firstwireless device.

Hereinafter, a processor for a first wireless device for indicatingsidelink radio link failure in a wireless communication system,according to some embodiments of the present disclosure, will bedescribed.

The processor may be configured to control the first wireless device toconfigure a maximum number of a counter for a PC5-Radio Resource Control(RRC) connection with a second wireless device. The processor may beconfigured to control the first wireless device to initialize thecounter to zero upon 1) establishing the PC5-RRC connection with thesecond wireless device, or 2) configuring or reconfiguring the maximumnumber of the counter. The processor may be configured to control thefirst wireless device to perform a transmission of a Medium AccessControl (MAC) Protocol Data Unit (PDU) to the second wireless devicebased on the established PC5-RRC connection. The processor may beconfigured to control the first wireless device to increase the counterbased on no reception of any acknowledgement to the transmission of theMAC PDU. The processor may be configured to control the first wirelessdevice to indicate Sidelink (SL) Radio Link Failure (RLF) for thePC5-RRC connection based on that the counter reaches the maximum numberof the counter.

According to some embodiments of the present disclosure, the processormay be configured to control the first wireless device to inform the SLRLF to the network.

According to some embodiments of the present disclosure, the processormay be configured to control the first wireless device to control an SLHybrid automatic repeat request (HARQ) entity of the first wirelessdevice to inform the SL RLF to an RRC entity of the first wirelessdevice.

According to some embodiments of the present disclosure, the processormay be configured to control the first wireless device to configure thecounter for each of multiple PC5-RRC connections with other wirelessdevices.

According to some embodiments of the present disclosure, the processormay be configured to control the first wireless device to configureanother counter for another PC5-RRC connection with a third wirelessdevice.

For example, the processor may be configured to control the firstwireless device to initialize the other counter to zero upon 1)establishing the other PC5-RRC connection with the third wirelessdevice, or 2) configuring or reconfiguring a maximum number of the othercounter for the other PC5-RRC connection with the third wireless device.

For example, a maximum number of the other counter for the other PC5-RRCconnection with the third wireless device may be same as the maximumnumber of the counter for the PC5-RRC connection with the secondwireless device.

According to some embodiments of the present disclosure, the processormay be configured to control the first wireless device to monitor eachPhysical Sidelink Feedback Channel (PSFCH) reception occasion associatedto the transmission of the MAC PDU. Based on that PSFCH reception isabsent on the PSFCH reception occasion, the processor may be configuredto control the first wireless device to increment the counter.

According to some embodiments of the present disclosure, the processormay be configured to control the first wireless device to re-initializethe counter to zero based on reception of any acknowledgement to thetransmission of the MAC PUD.

For example, the processor may be configured to control the firstwireless device to monitor each PSFCH reception occasion associated tothe transmission of the MAC PDU. Based on that PSFCH reception is notabsent on the PSFCH reception occasion, the processor may be configuredto control the first wireless device to re-initialize the counter tozero.

According to some embodiments of the present disclosure, thetransmission of the MAC PDU may include a PSSCH transmission for a pairof source layer-2 ID of the first wireless device and destination layer2-ID of the second wireless device corresponding to the PC5-RRCconnection.

According to some embodiments of the present disclosure, the processormay be configured to control the first wireless device to be incommunication with at least one of a user equipment, a network, or anautonomous vehicle other than the first wireless device.

Hereinafter, a non-transitory computer-readable medium has storedthereon a plurality of instructions for indicating sidelink radio linkfailure in a wireless communication system, according to someembodiments of the present disclosure, will be described.

According to some embodiment of the present disclosure, the technicalfeatures of the present disclosure could be embodied directly inhardware, in a software executed by a processor, or in a combination ofthe two. For example, a method performed by a wireless device in awireless communication may be implemented in hardware, software,firmware, or any combination thereof. For example, a software may residein RAM memory, flash memory, ROM memory, EPROM memory. EEPROM memory,registers, hard disk, a removable disk, a CD-ROM, or any other storagemedium.

Some example of storage medium is coupled to the processor such that theprocessor can read information from the storage medium. In thealternative, the storage medium may be integral to the processor. Theprocessor and the storage medium may reside in an ASIC. For otherexample, the processor and the storage medium may reside as discretecomponents.

The computer-readable medium may include a tangible and non-transitorycomputer-readable storage medium.

For example, non-transitory computer-readable media may include randomaccess memory (RAM) such as synchronous dynamic random access memory(SDRAM), read-only memory (ROM), non-volatile random access memory(NVRAM), electrically erasable programmable read-only memory (EEPROM),FLASH memory, magnetic or optical data storage media, or any othermedium that can be used to store instructions or data structures.Non-transitory computer-readable media may also include combinations ofthe above.

In addition, the method described herein may be realized at least inpart by a computer-readable communication medium that carries orcommunicates code in the form of instructions or data structures andthat can be accessed, read, and/or executed by a computer.

According to some embodiment of the present disclosure, a non-transitorycomputer-readable medium has stored thereon a plurality of instructions.The stored a plurality of instructions may be executed by a processor ofa first wireless device.

The stored a plurality of instructions may cause the first wirelessdevice to configure a maximum number of a counter for a PC5-RadioResource Control (RRC) connection with a second wireless device. Thestored a plurality of instructions may cause the first wireless deviceto initialize the counter to zero upon 1) establishing the PC5-RRCconnection with the second wireless device, or 2) configuring orreconfiguring the maximum number of the counter. The stored a pluralityof instructions may cause the first wireless device to perform atransmission of a Medium Access Control (MAC) Protocol Data Unit (PDU)to the second wireless device based on the established PC5-RRCconnection. The stored a plurality of instructions may cause the firstwireless device to increase the counter based on no reception of anyacknowledgement to the transmission of the MAC PDU. The stored aplurality of instructions may cause the first wireless device toindicate Sidelink (SL) Radio Link Failure (RLF) for the PC5-RRCconnection based on that the counter reaches the maximum number of thecounter.

According to some embodiments of the present disclosure, the stored aplurality of instructions may cause the first wireless device to informthe SL RLF to the network.

According to some embodiments of the present disclosure, the stored aplurality of instructions may cause the first wireless device to controlan SL Hybrid automatic repeat request (HARQ) entity of the firstwireless device to inform the SL RLF to an RRC entity of the firstwireless device.

According to some embodiments of the present disclosure, the stored aplurality of instructions may cause the first wireless device toconfigure the counter for each of multiple PC5-RRC connections withother wireless devices.

According to some embodiments of the present disclosure, the stored aplurality of instructions may cause the first wireless device toconfigure another counter for another PC5-RRC connection with a thirdwireless device.

For example, the stored a plurality of instructions may cause the firstwireless device to initialize the other counter to zero upon 1)establishing the other PC5-RRC connection with the third wirelessdevice, or 2) configuring or reconfiguring a maximum number of the othercounter for the other PC5-RRC connection with the third wireless device.

For example, a maximum number of the other counter for the other PC5-RRCconnection with the third wireless device may be same as the maximumnumber of the counter for the PC5-RRC connection with the secondwireless device.

According to some embodiments of the present disclosure, the stored aplurality of instructions may cause the first wireless device to monitoreach Physical Sidelink Feedback Channel (PSFCH) reception occasionassociated to the transmission of the MAC PDU. Based on that PSFCHreception is absent on the PSFCH reception occasion, the stored aplurality of instructions may cause the first wireless device toincrement the counter.

According to some embodiments of the present disclosure, the stored aplurality of instructions may cause the first wireless device tore-initialize the counter to zero based on reception of anyacknowledgement to the transmission of the MAC PUD.

For example, the stored a plurality of instructions may cause the firstwireless device to monitor each PSFCH reception occasion associated tothe transmission of the MAC PDU. Based on that PSFCH reception is notabsent on the PSFCH reception occasion, the stored a plurality ofinstructions may cause the first wireless device to re-initialize thecounter to zero.

According to some embodiments of the present disclosure, thetransmission of the MAC PDU may include a PSSCH transmission for a pairof source layer-2 ID of the first wireless device and destination layer2-ID of the second wireless device corresponding to the PC5-RRCconnection.

According to some embodiments of the present disclosure, the stored aplurality of instructions may cause the first wireless device to be incommunication with at least one of a user equipment, a network, or anautonomous vehicle other than the first wireless device.

Hereinafter, a method for indicating sidelink radio link failureperformed by a base station (BS) in a wireless communication system,according to some embodiments of the present disclosure, will bedescribed.

The BS may transmit, to a first wireless device, configuration for amaximum number of a counter for a PC5-Radio Resource Control (RRC)connection with a second wireless device. The BS may receive, from thefirst device, Sidelink (SL) Radio Link Failure (RLF) for the PC5-RRCconnection based on that the counter reaches the maximum number of thecounter.

Hereinafter, a base station (BS) for indicating sidelink radio linkfailure in a wireless communication system, according to someembodiments of the present disclosure, will be described.

The BS may include a transceiver, a memory, and a processor operativelycoupled to the transceiver and the memory.

The processor may be configured to control the transceiver to transmit,to a first wireless device, configuration for a maximum number of acounter for a PC5-Radio Resource Control (RRC) connection with a secondwireless device. The processor may be configured to control thetransceiver to receive, from the first device, Sidelink (SL) Radio LinkFailure (RLF) for the PC5-RRC connection based on that the counterreaches the maximum number of the counter.

The present disclosure can have various advantageous effects.

According to some embodiments of the present disclosure, a wirelessdevice could indicate sidelink (SL) radio link failure (RLF) in awireless communication system efficiently.

For example, a wireless device performing radio link management by usingHARQ feedback can properly detect radio link failure by considering HARQfeedback transmissions from another wireless device.

For example, a UE can properly detect radio link failure by consideringHARQ feedback transmissions from another UE when the UE establishes asidelink connection with a peer UE.

For example, a wireless communication system could properly provideradio link management for sidelink connection for a UE performing HARQtransmissions.

Advantageous effects which can be obtained through specific embodimentsof the present disclosure are not limited to the advantageous effectslisted above. For example, there may be a variety of technical effectsthat a person having ordinary skill in the related art can understandand/or derive from the present disclosure. Accordingly, the specificeffects of the present disclosure are not limited to those explicitlydescribed herein, but may include various effects that may be understoodor derived from the technical features of the present disclosure.

Claims in the present disclosure can be combined in a various way. Forinstance, technical features in method claims of the present disclosurecan be combined to be implemented or performed in an apparatus, andtechnical features in apparatus claims can be combined to be implementedor performed in a method. Further, technical features in method claim(s)and apparatus claim(s) can be combined to be implemented or performed inan apparatus. Further, technical features in method claim(s) andapparatus claim(s) can be combined to be implemented or performed in amethod. Other implementations are within the scope of the followingclaims.

What is claimed is:
 1. A method performed by a first wireless device ina wireless communication system, the method comprising, configuring amaximum number of a counter for a PC5-Radio Resource Control (RRC)connection with a second wireless device; initializing the counter tozero upon 1) establishing the PC5-RRC connection with the secondwireless device, or 2) configuring the maximum number of the counter;performing a Physical Sidelink Shared Channel (PSSCH) transmission tothe second wireless device based on the established PC5-RRC connection;increasing the counter based on no Physical Sidelink Feedback Channel(PSFCH) reception associated with the PSSCH transmission; declaringSidelink (SL) Radio Link Failure (RLF) for the PC5-RRC connection basedon that the counter reaches the maximum number of the counter; andinforming the network of the SL RLF for the PC5-RRC connection.
 2. Themethod of claim 1, wherein the method further comprises, indicating, bya SL Hybrid automatic repeat request (HARQ) entity of the first wirelessdevice to an RRC entity of the first wireless device, the SL RLF basedon that the counter reaches the maximum number of the counter.
 3. Themethod of claim 1, wherein the method further comprises, configuring thecounter for each of multiple PC5-RRC connections with other wirelessdevices.
 4. The method of claim 1, wherein the method further comprises,configuring another counter for another PC5-RRC connection with a thirdwireless device.
 5. The method of claim 4, wherein the method furthercomprises, initializing the other counter to zero upon 1) establishingthe other PC5-RRC connection with the third wireless device, or 2)configuring a maximum number of the other counter for the other PC5-RRCconnection with the third wireless device.
 6. The method of claim 4,wherein a maximum number of the other counter for the other PC5-RRCconnection with the third wireless device is same as the maximum numberof the counter for the PC5-RRC connection with the second wirelessdevice.
 7. The method of claim 1, wherein the increasing the counterfurther comprises, monitoring each PSFCH reception occasion associatedwith the PSSCH transmission; and based on that PSFCH reception is absenton the PSFCH reception occasion, incrementing the counter.
 8. The methodof claim 1, wherein the method further comprises, re-initializing thecounter to zero based on PSFCH reception associated with the PSSCHtransmission.
 9. The method of claim 8, wherein the re-initializing thecounter to zero further comprises, monitoring each PSFCH receptionoccasion associated to the PSSCH transmission; and based on that thePSFCH reception is not absent on the PSFCH reception occasion,re-initializing the counter to zero.
 10. The method of claim 1, whereinthe PSSCH transmission includes a PSS CH transmission for a pair ofsource layer-2 ID of the first wireless device and destination layer2-ID of the second wireless device corresponding to the PC5-RRCconnection.
 11. The method of claim 1, wherein the first wireless deviceis in communication with at least one of a user equipment, a network, oran autonomous vehicle other than the first wireless device.
 12. A firstwireless device in a wireless communication system comprising: atransceiver; a memory; and at least one processor operatively coupled tothe transceiver and the memory, and configured to: configure a maximumnumber of a counter for a PC5-Radio Resource Control (RRC) connectionwith a second wireless device; initialize the counter to zero upon 1)establishing the PC5-RRC connection with the second wireless device, or2) configuring the maximum number of the counter; control thetransceiver to perform a Physical Sidelink Shared Channel (PSSCH)transmission to the second wireless device based on the establishedPC5-RRC connection; increase the counter based on no Physical SidelinkFeedback Channel (PSFCH) reception associated with the PSSCHtransmission; and declare Sidelink (SL) Radio Link Failure (RLF) for thePC5-RRC connection based on that the counter reaches the maximum numberof the counter; and control the transceiver to inform the network of theSL RLF for the PC5-RRC connection.
 13. The first wireless device ofclaim 12, wherein the at least one processor is further configured to,control an SL Hybrid automatic repeat request (HARQ) entity of the firstwireless device to indicate the SL RLF to an RRC entity of the firstwireless device based on that the counter reaches the maximum number ofthe counter.
 14. The first wireless device of claim 12, wherein the atleast one processor is further configured to, configure the counter foreach of multiple PC5-RRC connections with other wireless devices. 15.The first wireless device of claim 12, wherein the at least oneprocessor is further configured to, configure another counter foranother PC5-RRC connection with a third wireless device.
 16. The firstwireless device of claim 15, wherein the at least one processor isfurther configured to, initialize the other counter to zero upon 1)establishing the other PC5-RRC connection with the third wirelessdevice, or 2) configuring a maximum number of the other counter for theother PC5-RRC connection with the third wireless device.
 17. The firstwireless device of claim 15, wherein a maximum number of the othercounter for the other PC5-RRC connection with the third wireless deviceis same as the maximum number of the counter for the PC5-RRC connectionwith the second wireless device.
 18. A non-transitory computer-readablemedium having stored thereon a plurality of instructions, which, whenexecuted by a processor of a first wireless device, cause the firstwireless device to: configure a maximum number of a counter for aPC5-Radio Resource Control (RRC) connection with a second wirelessdevice; initialize the counter to zero upon 1) establishing the PC5-RRCconnection with the second wireless device, or 2) configuring themaximum number of the counter; perform a Physical Sidelink SharedChannel (PSSCH) transmission to the second wireless device based on theestablished PC5-RRC connection; increase the counter based on noPhysical Sidelink Feedback Channel (PSFCH) reception associated with thePSSCH transmission; and declaring Sidelink (SL) Radio Link Failure (RLF)for the PC5-RRC connection based on that the counter reaches the maximumnumber of the counter; and informing the network of the SL RLF for thePC5-RRC connection.